[codex] Add workspace diff viewer plugin (#6071)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies.
> - Operators need to inspect what agents changed inside execution and
project workspaces.
> - The existing workspace detail views did not provide a first-party
rich diff surface for staged, unstaged, head, renamed, binary,
oversized, and untracked changes.
> - The plugin system is the intended extension point for optional rich
UI surfaces.
> - This pull request adds a workspace diff plugin plus host services
and shared contracts so Changes tabs can render workspace diffs through
plugin slots.
> - The diff-renderer dependency should stay owned by the plugin package
rather than the core UI app.
> - The dependency surface must stay aligned with repository PR policy,
including intentionally omitting `pnpm-lock.yaml` from the PR.
> - The benefit is a more reviewable workspace surface without
hard-coding the renderer into every page.

## What Changed

- Added `@paperclipai/plugin-workspace-diff`, including diff
normalization, plugin manifest/worker/UI entrypoints, and focused plugin
tests.
- Kept `@pierre/diffs` scoped to `@paperclipai/plugin-workspace-diff`;
removed the core UI lab diff-renderer surface and direct UI package
dependency.
- Added shared workspace diff types and validators, plus plugin SDK
surface for workspace diff host services.
- Added server workspace diff service support and route coverage for
execution/project workspace diff flows.
- Wired Execution Workspace and Project Workspace Changes tabs to load
the diff plugin, including loading/error fallback behavior.
- Added UI tests and fixtures for the Changes tabs and plugin bridge
behavior.
- Added the new plugin package manifest to the Docker deps stage so PR
policy can validate dependency coverage.
- Addressed review hardening around empty untracked patches, workspace
path exposure, project workspace read capability checks, and default
base refs.

## Verification

- `pnpm --filter @paperclipai/plugin-workspace-diff test`
- `pnpm exec vitest run
packages/shared/src/validators/workspace-diff.test.ts
server/src/__tests__/workspace-diff-service.test.ts
ui/src/pages/ProjectWorkspaceDetail.test.tsx
ui/src/pages/ExecutionWorkspaceDetail.test.tsx`
- `pnpm exec vitest run ui/src/plugins/bridge.test.ts
server/src/__tests__/workspace-runtime-routes-authz.test.ts`
- `pnpm --filter @paperclipai/shared typecheck`
- `pnpm --filter @paperclipai/plugin-workspace-diff typecheck`
- `pnpm --filter @paperclipai/server typecheck`
- `pnpm --filter @paperclipai/ui typecheck`
- `node ./scripts/check-docker-deps-stage.mjs`
- Browser screenshot captured from the local worktree dev server:
https://files.catbox.moe/ofdpsp.png
- Confirmed branch is rebased onto `public-gh/master`,
`.github/workflows/pr.yml` is not included in the PR diff,
`ui/package.json` is not included in the PR diff, and `pnpm-lock.yaml`
is not included in the PR diff.

## Risks

- Medium UI integration risk: the Changes tab depends on the plugin slot
and host diff service path.
- Medium dependency risk: this adds `@pierre/diffs` in the plugin
package, but `pnpm-lock.yaml` is intentionally omitted per packaging
instructions because repository automation manages lockfile updates.
- Current CI blocker: downstream frozen installs fail until the
repository policy path for new plugin package dependencies is chosen.
- Diff rendering edge cases are covered for common working-tree and head
diff states, but very large repositories may still expose performance
limits.
- No migrations are included.

> 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, GPT-5 class coding model, tool-enabled local execution
environment. Exact context window was not exposed by the runtime.

## 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 run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

server/src/services/recovery/service.ts

@@ -2970,6 +2970,28 @@ export function recoveryService(db: Db, deps: { enqueueWakeup: RecoveryWakeup })
     return result;
   }
 
+  async function retireDoneLivenessRecoveryBlockers() {
+    const closedRecoveries = await db
+      .select()
+      .from(issues)
+      .where(
+        and(
+          eq(issues.originKind, RECOVERY_ORIGIN_KINDS.issueGraphLivenessEscalation),
+          isNull(issues.hiddenAt),
+          inArray(issues.status, ["done", "cancelled"]),
+        ),
+      );
+
+    let blockerRelationsRemoved = 0;
+    for (const recovery of closedRecoveries) {
+      if (await removeRecoveryBlockerFromSource(recovery)) {
+        blockerRelationsRemoved += 1;
+      }
+    }
+
+    return { blockerRelationsRemoved };
+  }
+
   function normalizeIssueGraphLivenessAutoRecoveryLookbackHours(raw: unknown) {
     const numeric = Math.floor(asNumber(raw, DEFAULT_ISSUE_GRAPH_LIVENESS_AUTO_RECOVERY_LOOKBACK_HOURS));
     return Math.min(
@@ -3365,6 +3387,7 @@ export function recoveryService(db: Db, deps: { enqueueWakeup: RecoveryWakeup })
     const now = new Date();
     const cutoff = new Date(now.getTime() - lookbackHours * 60 * 60 * 1000);
     const obsoleteRecoveryCleanup = await retireObsoleteLivenessRecoveryIssues(findings);
+    const doneRecoveryBlockerCleanup = await retireDoneLivenessRecoveryBlockers();
     const updatedAtByIssueKey = await loadLivenessDependencyUpdatedAtByIssue(findings);
     const result = {
       findings: findings.length,
@@ -3379,6 +3402,7 @@ export function recoveryService(db: Db, deps: { enqueueWakeup: RecoveryWakeup })
       obsoleteRecoveriesRetired: obsoleteRecoveryCleanup.retired,
       obsoleteRecoveriesActiveSkipped: obsoleteRecoveryCleanup.activeSkipped,
       obsoleteRecoveryBlockerRelationsRemoved: obsoleteRecoveryCleanup.blockerRelationsRemoved,
+      doneRecoveryBlockerRelationsRemoved: doneRecoveryBlockerCleanup.blockerRelationsRemoved,
       issueIds: [] as string[],
       escalationIssueIds: [] as string[],
       retiredRecoveryIssueIds: obsoleteRecoveryCleanup.retiredIssueIds,