Add experimental Paperclip Notebook MCP connection (#16984)

## Thinking Path

> - Paperclip connects agents to external tools through saved accounts
and per-action permissions.
> - Notebook exposes artifact management through an ordinary remote MCP
server with OAuth.
> - A private pilot needs a hidden, default-off catalog and execution
gate.
> - Local file publishing belongs to Notebook, which can accept bounded
file bytes through ordinary MCP tools.
> - Paperclip therefore needs the connector registration and generic
availability checks, with no file-transfer architecture.

## Linked Issues or Issue Description

**Subsystem affected**

Apps catalog, experimental feature metadata, connection setup, and
connector availability.

**Problem or motivation**

Users need to connect Notebook as their Cloud account, assign its tools
to agents, and retain Paperclip's normal Allowed / Ask first / Off
rules. The private pilot must remain hidden until an operator enables
it. Notebook should own its upload protocol and local publishing script.

**Proposed solution**

Register a personal remote MCP OAuth connection at Notebook's canonical
endpoint. Reuse existing OAuth discovery, credential storage, refresh,
reconnect, and removal. Enforce availability through generic catalog
feature metadata and saved application identity. Keep Notebook's
standalone uploader in its own service repository; it calls the ordinary
gateway and receives no saved OAuth credential.

**Alternatives considered**

A gallery-only filter permits retained tools and deep links while
disabled. A shared workspace publisher and private upload-ticket
transport add runtime behavior that a normal MCP connector does not
require. Notebook can receive file bytes directly through its own tools
instead.

**Roadmap alignment**

This extends Connected Apps and supports Artifacts and Work Products.
ROADMAP.md and related PRs were checked. This PR is standalone on
master. The separate OAuth lifecycle and file-transfer proposals (#17085
and #17086) are closed and are not dependencies.

## What Changed

- Register Notebook's personal MCP OAuth method, canonical endpoint,
scopes, catalog metadata, and branding.
- Declare managed `enablePaperclipNotebook` with false defaults and no
user-facing settings toggle or staging opt-in.
- Use generic availability metadata for gallery/setup, retained
connection identity, OAuth completion, health, tool/context discovery,
and dispatch. Resources/prompts recheck before credentials, including
retained handles. Removal remains available while disabled.
- Resolve catalog application identity from the saved application key,
so editable connection labels cannot bypass the hidden gate.
- Select a method's sole supported credential kind when no kind is
supplied.
- Keep UI changes to metadata-driven availability and existing
setup/reconnect controls.
- Document Notebook's service-owned upload script, inline publication,
ordinary action policies, and credential behavior.
- Add ordinary MCP OAuth, assignment, action-policy, disabled-state,
settings, and catalog tests.

No workspace contribution registry, private transfer endpoint, native
publisher, Runner file-reader change, or Paperclip CLI upload command is
included. The entire native-runtime and CLI trees match master. Upload
code lives in `paperclip-cloud/notebook/`.

## Verification

Source head: `65ef741e4f476c67425b57d2fb2d6d4c00e99b06`, directly on
master `53732c811bb69655eb43d3d12f2063ae4ca5ad67`. The diff is 42 files.
Shared execution changes only enforce generic catalog availability; tool
access also resolves saved application identity and the sole supported
credential kind. Neither module contains Notebook upload logic.

- Catalog/shared/settings/UI suites: 592 tests passed across 12 files.
Shared/server/UI typechecks passed using installed compilers.
- Fresh real PostgreSQL generic MCP suite: 84/84 passed at final source;
server typecheck and module boundaries pass. Coverage includes personal
OAuth, ordinary refresh/reconnect, assignments, Allowed / Ask first /
Off, hidden feature enforcement, and local credential removal. Four new
resources/prompts cases failed against the prior code and pass after
filtering saved application identity and rechecking before credentials.
They prove missing/relabelled setup markers and stale eligibility cannot
dispatch or read secrets while disabled; an ordinary provider remains
available with the flag off.
- The full tool-access service suite passed 463/464 cases. One unchanged
Google Workspace `slides.write` case timed out at 15 seconds; it passed
on one isolated retry without source or timeout changes. Its exact test
block matches master. The cause is not established; final-head CI must
qualify the complete suite.
- Maps, module boundaries, token gates, and whitespace checks passed.
Byte comparisons confirm the former transfer/runtime/CLI surfaces match
master.
- Fresh exact-head Greptile is 5/5 with zero unresolved findings after
an exhaustive feedback audit. Current-head CI workflow
[39625691137](https://github.com/paperclipai/paperclip/actions/runs/39625691137)
succeeded, including both required checks (`ci / verify`, `ci / e2e`),
Build, and browser E2E. Supplementary security/advisory scan status is
recorded in the PR Checks panel and qualification receipt; prior-head
scans are not counted. The superseded `4bd7af9b2e` completed CI
successfully, but Greptile found the valid resources/prompts
availability gap described above. It was fixed, replied to, and
resolved; earlier-head results do not qualify this revision.

Preserved environment failures: the first socket-restricted UI/route run
had 93 listener setup failures, and the same 93 cases passed with
local-socket access. The package-manager launcher could not fetch its
signature metadata; installed compilers passed without dependency or
configuration changes. The full service timeout and isolated retry
remain recorded separately. The superseded `585e870e73` CI also failed
an unchanged agent-chat project-plan revision assertion after task
creation; the complete spec and relevant runtime sources match master,
and a same-master prior run passed. Its cause is not established. Logs
are preserved; no test or timeout was weakened and no old-head rerun was
requested. The subsequent heads run full CI independently; no prior-head
pass substitutes for current qualification.

The Notebook uploader requires a separate service release. This public
PR adds no uploader runtime to Paperclip and claims no newly deployed
browser/agent acceptance. The Notebook-owned upload path is qualified
separately. Code-owner review remains required before merge.

## Risks

- The feature flag gates the curated connector; it does not create a
Notebook service-side team allowlist or block arbitrary standard MCP
URLs.
- Publishing, sharing, and deletion retain the existing assignment and
action-policy boundaries.
- The hidden feature must be checked for retained tools and saved
identity, including when connection labels change.
- Disconnect removes local credentials. It does not revoke the remote
Notebook authorization; the owner can revoke it in Notebook.
- Ordinary refresh uses the existing client. A lost response after
refresh-token rotation can require reconnect.
- The standalone Notebook script and its bounded upload tools must ship
together in the Notebook service before that documented convenience path
is available.
- No database schema, workflow, lockfile, shared transfer, or Runner
change is included. No merge, deployment, or rollout is performed by
this update.

## Model Used

OpenAI GPT-6 in Codex, with reasoning, repository inspection, code
execution, and tool use. The runtime did not expose a more specific
model ID or context-window size.

## 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
- [x] All Paperclip CI gates are green
- [x] 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: Paperclip <noreply@paperclip.ing>

scripts/app-definition-overrides/paperclip-notebook.json

@@ -0,0 +1,50 @@
+{
+  "schemaVersion": 1,
+  "slug": "paperclip-notebook",
+  "experimentalFeatureKey": "enablePaperclipNotebook",
+  "name": "Paperclip Notebook",
+  "description": "Publish, find, and share reports, files, and interactive pages with your Paperclip Cloud account.",
+  "categories": [
+    "content",
+    "productivity"
+  ],
+  "featured": true,
+  "branding": {
+    "logoUrl": "/brands/apps/paperclip-notebook.svg",
+    "darkLogoUrl": "/brands/apps/paperclip-notebook-dark.svg"
+  },
+  "urlPatterns": [
+    "https://notebook.paperclip.app/*"
+  ],
+  "availability": {
+    "available": true
+  },
+  "methods": [
+    {
+      "key": "mcp-oauth",
+      "transport": "mcp_remote",
+      "auth": "oauth",
+      "ownershipModes": [
+        "dcr"
+      ],
+      "oauthClientRegistration": "dcr",
+      "grantKinds": [
+        "user"
+      ],
+      "whenToUse": "Sign in with Paperclip Cloud and let your assigned agents publish and manage your Notebook pages.",
+      "defaults": {
+        "serverUrl": "https://notebook.paperclip.app/mcp",
+        "scopesHint": [
+          "notebook:read",
+          "notebook:write",
+          "notebook:share",
+          "notebook:delete"
+        ],
+        "mcpSessionRequired": true
+      },
+      "guidanceMd": "Connect your Paperclip Cloud account. Assigned agents can read available pages, publish and update your pages, change sharing including making pages public, manage versions, and delete or restore your pages. Manage individual actions in Permissions.",
+      "riskTier": "S3"
+    }
+  ],
+  "redirectConstraints": "https-or-loopback-http"
+}