feat(ui): single-source design tokens, visual regression suite, and theme retune (#9134)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - Its UI is the operator's daily surface: task lists, boards, budgets,
agent status — all built on shadcn components and Tailwind
> - Visual values (colors, spacing, type sizes, radii) were hardcoded at
~1,600 call sites: the same "small gray label" was 9/10/11px depending
on the file, charts disagreed with chips about status colors, two
toggle-switch implementations coexisted in two greens, and there was no
visual regression coverage
> - This made the UI drift-prone and made any restyle a
hundreds-of-files project, which discourages design iteration
> - This pull request extracts visual values into a single token layer
in `ui/src/index.css`, adds a Storybook visual regression suite backed
by external immutable baseline archives, and then applies a deliberate
retune reviewed change-by-change on screenshot diffs
> - The benefit is that Paperclip's look becomes a config surface:
retheming is a token edit reviewed as a snapshot diff, drift is blocked
by a token gate, and future UI PRs can prove exactly what changed
visually without committing hundreds of PNGs

## Linked Issues or Issue Description

No existing public issue covers this work (searched "design tokens",
"visual regression", "design system" across issues and PRs). Related in
spirit: Refs #8982 (theming a hardcoded panel — a one-off instance of
the same problem class this PR addresses systematically).

**Problem (feature-request form):** UI visual values are hardcoded per
call site with no source of truth and no regression coverage;
consistency depends on reviewer memory, and restyling requires mass file
edits.
**Proposed solution (this PR):** a single token layer + enforcement gate
+ externally stored visual snapshot suite, then an intentional restyle
on top of that foundation.

## What Changed

- **Token extraction (zero visual change, machine-verified during
development):** committed codemods (`scripts/codemod-*.mjs`) moved
~1,600 hardcoded color/type/spacing/radius/shadow/misc values into named
tokens in a non-inline `:root` block of `ui/src/index.css`.
- **Visual regression suite:** `pnpm test:storybook-visual` covers 255
stories × light/dark = 510 Playwright screenshots at `maxDiffPixels: 0`,
plus new primitive-coverage stories and deterministic-render fixes.
- **External visual baselines:** committed PNG snapshots were removed.
`tests/storybook-visual/baseline-manifest.json` pins an immutable
archive URL/hash/size/count, and `scripts/storybook-visual-baseline.mjs`
handles `download`, `verify`, `pack`, and trusted maintainer `upload`
flows.
- **Opt-in visual CI artifacts:** added a `Storybook Visual` workflow
that runs on manual dispatch or PRs labeled `storybook-visual`,
downloads/verifies the baseline, runs Playwright, and uploads Playwright
report/test-result artifacts for review. Normal PR runs do not mutate
baseline objects.
- **Token gate:** `pnpm check:token-gates` — zero hex literals, zero
arbitrary bracket values, zero raw font-sizes in `ui/src/components/**`
and `ui/src/pages/**`, with a documented inline allowlist for legitimate
opt-outs.
- **Theme retune (intentional, snapshot-reviewed):** new base theme
values; radius ladder derived from a single `--radius` knob; micro-type
cluster collapsed to a named ladder (`--text-nano/micro/compact` +
Tailwind `text-xs`/`text-sm`); letter-spacing collapsed to named steps.
- **One status-color vocabulary:** charts, quota/budget bar fills,
RUNNING/live chips, and liveness indicators all use the canonical
`--status-*` hues. Light-mode legibility fixes for red alert surfaces
that used dark-tuned text classes.
- **One switch:** `ToggleSwitch` restyled to the registry capsule form,
second hand-rolled implementation removed, and all call sites unified.
- **Docs:** `DESIGN.md` is the design contract; `doc/design/` holds
audit reports, decision logs, and updated guidance for external baseline
review/update workflows.
- Dead code removed (`agentStatusBadge` duplicate map), byte-identical
contrast constants consolidated, semantic renames
(`--project-seed`/`--project-none`, `--liveness-blue`).

## Verification

- `pnpm check:token-gates` — 3/3 gates CLEAN during the design-system
run
- `pnpm typecheck` && `pnpm --filter @paperclipai/ui build` — green
during the design-system run
- `node --test scripts/__tests__/storybook-visual-baseline.test.mjs` —
pass after external-baseline rework
- `pnpm exec tsc --noEmit --pretty false --module NodeNext
--moduleResolution NodeNext --target ES2022 --types
node,@playwright/test tests/storybook-visual/playwright.config.ts
tests/storybook-visual/storybook-visual.spec.ts` — pass after
external-baseline rework
- `git diff --check origin/pr/9134..HEAD` — pass after external-baseline
rework
- `find tests/storybook-visual -type f -name '*.png' -print | wc -l` —
`0`
- `node scripts/storybook-visual-baseline.mjs verify` — intentionally
fails closed until the first trusted maintainer publishes the baseline
archive and updates `baseline-manifest.json`

## Risks

- **Large but shallow:** the PR still touches many UI files due to
mechanical token extraction and retune work, but committed PNG snapshot
churn has been removed from the branch.
- **Baseline publication required before the visual suite can pass in
clean clones:** the manifest currently has placeholder archive metadata.
A trusted maintainer must publish the first immutable archive, then
update `baseline-manifest.json`.
- **Rendering platform variance:** the external baseline should be
captured in the documented Linux/Chromium environment. Future CI runs
verify against the pinned archive and fail closed on checksum/count
mismatch.
- **Visual CI is opt-in while stabilizing:** add the `storybook-visual`
label or dispatch the workflow manually to produce downloadable
Playwright report/test-result artifacts.
- **Scheduled follow-ups, deliberately out of scope:** Tailwind palette
classes map to semantic tokens in a dedicated pass; card/pill component
consolidation; ESLint ratchet. Tracked in
`doc/design/DECISION-SHEET.md`.

## Model Used

Claude Fable 5 (Anthropic, `claude-fable-5`, Mythos-class tier) with
extended thinking, running in Claude Code with tool use; mechanical
phases delegated to Claude Sonnet subagents. Follow-up external-baseline
rework assisted by OpenAI Codex (`gpt-5` coding agent with repository,
terminal, and GitHub tool use). All bulk rewrites executed via
deterministic, idempotent scripts committed in `scripts/`; intentional
visual changes were human-reviewed on screenshot contact sheets.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run targeted local verification and documented the
intentional baseline-publication failure above
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green *(pending new CI run after this
rework)*
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
*(pending review)*
- [x] I will address all Greptile and reviewer comments before
requesting merge

🤖 Generated with [Claude Code](https://claude.com/claude-code) and
OpenAI Codex

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Dotta <bippadotta@protonmail.com>
Co-authored-by: Paperclip <noreply@paperclip.ing>

ui/src/components/DocumentDiffModal.tsx

@@ -73,8 +73,8 @@ export function DocumentDiffModal({
 
   const lineClassesByKind: Record<DiffRow["kind"], string> = {
     context: "bg-transparent",
-    removed: "bg-red-500/10 text-red-100",
-    added: "bg-green-500/10 text-green-100",
+    removed: "bg-red-500/10 text-red-900 dark:text-red-100",
+    added: "bg-green-500/10 text-green-900 dark:text-green-100",
   };
 
   const markerByKind: Record<DiffRow["kind"], string> = {
@@ -85,7 +85,7 @@ export function DocumentDiffModal({
 
   return (
     <Dialog open={open} onOpenChange={onOpenChange}>
-      <DialogContent className="!max-w-[90%] w-full max-h-[85vh] overflow-hidden flex flex-col">
+      <DialogContent className="!max-w-(--pct-90) w-full max-h-(--sz-85vh) overflow-hidden flex flex-col">
         <div className="flex items-center justify-between gap-4">
           <DialogHeader className="shrink-0">
             <DialogTitle>
@@ -95,7 +95,7 @@ export function DocumentDiffModal({
 
           <div className="flex items-center gap-4 shrink-0">
             <div className="flex items-center gap-2">
-              <span className="rounded-full border border-red-500/30 bg-red-500/10 px-2 py-0.5 text-[10px] font-medium uppercase tracking-wider text-red-400">Old</span>
+              <span className="rounded-full border border-red-500/30 bg-red-500/10 px-2 py-0.5 text-(length:--text-nano) font-medium uppercase tracking-wider text-red-400">Old</span>
               <Select
                 value={effectiveLeftId ?? ""}
                 onValueChange={(value) => setLeftRevisionId(value)}
@@ -113,7 +113,7 @@ export function DocumentDiffModal({
               </Select>
             </div>
             <div className="flex items-center gap-2">
-              <span className="rounded-full border border-green-500/30 bg-green-500/10 px-2 py-0.5 text-[10px] font-medium uppercase tracking-wider text-green-400">New</span>
+              <span className="rounded-full border border-green-500/30 bg-green-500/10 px-2 py-0.5 text-(length:--text-nano) font-medium uppercase tracking-wider text-green-400">New</span>
               <Select
                 value={effectiveRightId ?? ""}
                 onValueChange={(value) => setRightRevisionId(value)}
@@ -141,8 +141,8 @@ export function DocumentDiffModal({
           ) : leftRevision.id === rightRevision.id ? (
             <div className="p-6 text-center text-muted-foreground text-sm">Both sides are the same revision.</div>
           ) : (
-            <div className="font-mono text-[12px] leading-6">
-              <div className="grid grid-cols-[56px_56px_24px_minmax(0,1fr)] border-b border-border/60 bg-muted/30 px-3 py-2 text-[11px] uppercase tracking-wide text-muted-foreground">
+            <div className="font-mono text-xs leading-6">
+              <div className="grid grid-cols-(--gtc-1) border-b border-border/60 bg-muted/30 px-3 py-2 text-(length:--text-micro) uppercase tracking-wide text-muted-foreground">
                 <span>Old</span>
                 <span>New</span>
                 <span />
@@ -151,7 +151,7 @@ export function DocumentDiffModal({
               {diffRows.map((row, index) => (
                 <div
                   key={`${row.kind}-${index}-${row.oldLineNumber ?? "x"}-${row.newLineNumber ?? "x"}`}
-                  className={`grid grid-cols-[56px_56px_24px_minmax(0,1fr)] gap-0 border-b border-border/30 px-3 ${lineClassesByKind[row.kind]}`}
+                  className={`grid grid-cols-(--gtc-1) gap-0 border-b border-border/30 px-3 ${lineClassesByKind[row.kind]}`}
                 >
                   <span className="select-none border-r border-border/30 pr-3 text-right text-muted-foreground">
                     {row.oldLineNumber ?? ""}