feat(ui): refine the chat-style task workflow (#11263)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work.
> - The issue detail view is the main place where people read work and
guide agents.
> - The chat-style task view needs clear messages, controls, properties,
and document feedback.
> - Dense metadata and disconnected controls make active work harder to
scan.
> - This pull request refines the existing chat-style task workflow
across desktop and mobile layouts.
> - The benefit is a clearer issue thread with faster access to the
controls that guide work.

## Linked Issues or Issue Description

**What existing behavior does this improve?**

The change improves the chat-style issue detail view that was introduced
in [#10606](https://github.com/paperclipai/paperclip/pull/10606) and
expanded in
[#10707](https://github.com/paperclipai/paperclip/pull/10707).

**Current behavior**

The issue thread spreads task controls across the page. Agent-turn
metadata competes with the message content. Document annotation comments
use inline placement that limits the document reading area. The mobile
composer can overlap the bottom navigation.

**Proposed behavior**

The issue view keeps the thread focused on message content. It moves
supporting controls into the properties area, adds searchable
assignment, restores the sub-task tree, docks document comments in a
side gutter, and keeps the mobile composer clear of navigation.

**Reason and benefit**

People can scan active work faster and find task controls without
leaving the issue. The layout also gives documents and mobile
conversations more usable space.

**Breaking changes**

None. The change updates presentation and interaction behavior in the
existing issue UI.

## What Changed

- Refined task-chat message spacing, metadata, agent bubbles, and
composer alignment.
- Added searchable assignment and restored sub-task navigation in the
properties pane.
- Moved document annotation comments into a right-side gutter.
- Kept the mobile composer above the auto-hiding bottom navigation.
- Added and updated focused component tests for the changed
interactions.

## Verification

- `pnpm check:token-gates`
- `TZ=UTC pnpm --filter @paperclipai/ui exec vitest run
src/components/InlineEntitySelector.test.tsx
src/components/IssueDocumentAnnotations.test.tsx
src/components/IssueProperties.test.tsx
src/components/TaskChatThread.test.tsx src/pages/IssueDetail.test.tsx`
- The token gates report 3/3 clean.
- The focused test run passes 124 tests in 5 files.
- Visual snapshot baselines were not updated. This follows the
`doc/design/DECISION-SHEET.md` entry "Per-change snapshot verification
demoted to dormant (Jul 13 2026)."

## Risks

- The changes affect several related issue-detail layouts. A browser
review should cover desktop and mobile widths before merge.
- The monitor-row test formats time in the host timezone. The
verification command sets `TZ=UTC` to match CI.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex with GPT-5. The context-window size is not exposed in
this environment. The model used reasoning, repository tools, code
execution, and GitHub tools.

## 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 tests locally and they pass
- [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
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Paperclip <noreply@paperclip.ing>

ui/src/components/task-chat/transcript-adapter.test.ts

@@ -375,15 +375,35 @@ describe("settledRunChildren (PAP-361)", () => {
   ];
   const parsed = transcriptToTaskChatItems(transcript, { runId: "run-1", running: false });
 
-  it("keeps exactly the tool rows — messages AND thinking are excluded", () => {
+  it("groups tools under the historical assistant boundary and excludes the final reply", () => {
     const children = settledRunChildren(parsed);
-    expect(children.map((c) => c.kind)).toEqual(["tool", "tool"]);
+    expect(children.map((c) => c.kind)).toEqual(["activity_phase"]);
+    const phase = children[0];
+    expect(phase.kind === "activity_phase" && phase.interstitial?.text).toBe("Checking the adapter first.");
+    expect(phase.kind === "activity_phase" && phase.items.map((item) => item.kind)).toEqual(["tool", "tool"]);
   });
 
   it("matches the folded summary's tool count exactly (row-count parity)", () => {
     const children = settledRunChildren(parsed);
     const summary = buildTurnSummary(transcript);
-    expect(children.filter((c) => c.kind === "tool")).toHaveLength(summary.toolCount);
+    const phaseToolCount = children.reduce(
+      (count, child) => count + (child.kind === "activity_phase" ? child.items.filter((item) => item.kind === "tool").length : 0),
+      0,
+    );
+    expect(phaseToolCount).toBe(summary.toolCount);
+  });
+
+  it("creates a stable opening phase for calls before the first interstitial", () => {
+    const opening = transcriptToTaskChatItems([
+      toolCall("Read", { file_path: "a.ts" }),
+      { kind: "assistant", ts: TS, text: "Now editing." } as TranscriptEntry,
+      toolCall("Edit", { file_path: "a.ts" }),
+      { kind: "assistant", ts: TS, text: "Done." } as TranscriptEntry,
+    ], { runId: "run-opening", running: false });
+    const phases = settledRunChildren(opening);
+    expect(phases).toHaveLength(2);
+    expect(phases[0].id).toContain(":phase:opening");
+    expect(phases[1].kind === "activity_phase" && phases[1].summary).toBe("Edited 1 file");
   });
 });