Show workspace changes and stale notices in issue threads (#5356)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - The issue thread is the operator's durable audit trail for what
changed and why
> - Workspace changes and stale disposition notices need to be visible
in that same timeline without noisy or misleading rendering
> - The local branch already contained backend activity details,
timeline conversion, and UI rendering work for those events
> - This pull request isolates the issue-thread activity work into a
standalone branch against `origin/master`
> - The benefit is a focused audit-trail PR that can merge independently
of the sidebar/operator UI polish branch

## What Changed

- Adds readable workspace-change activity details to issue update
activity events.
- Surfaces workspace-change events in issue chat/timeline rendering.
- Makes the existing issue comment migration idempotent.
- Folds and renders stale disposition notices inline so they match
activity-log styling and spacing.
- Adds focused route, timeline, and issue-thread system notice coverage.

## Verification

- `pnpm install --frozen-lockfile`
- `pnpm exec vitest run
server/src/__tests__/issue-activity-events-routes.test.ts
ui/src/lib/issue-timeline-events.test.ts
ui/src/components/IssueChatThreadSystemNotice.test.tsx` — 3 files
passed, 22 tests passed.
- Confirmed the PR changes 9 files and does not include `pnpm-lock.yaml`
or `.github/workflows/*`.
- `pnpm exec vitest run
server/src/__tests__/issue-closed-workspace-routes.test.ts` — 1 file
passed, 4 tests passed.
- `pnpm exec vitest run
server/src/__tests__/issue-activity-events-routes.test.ts
ui/src/lib/issue-timeline-events.test.ts
ui/src/components/IssueChatThreadSystemNotice.test.tsx
server/src/services/recovery/successful-run-handoff.test.ts
packages/shared/src/validators/issue.test.ts` — 5 files passed, 54 tests
passed.
- `pnpm --filter @paperclipai/shared typecheck && pnpm --filter
@paperclipai/server typecheck && pnpm --filter @paperclipai/ui
typecheck`.
- `pnpm --filter @paperclipai/ui typecheck` after adding the Storybook
screenshot fixture.
- Captured Storybook screenshots for the new UI rendering paths:
- Collapsed stale notice + workspace-change row:
`docs/pr-screenshots/pr-5356/issue-thread-notices-collapsed.png`
- Expanded stale notice details:
`docs/pr-screenshots/pr-5356/issue-thread-notices-expanded.png`


### Screenshots

Collapsed stale notice with workspace-change row:

![Collapsed stale notice with workspace-change
row](docs/pr-screenshots/pr-5356/issue-thread-notices-collapsed.png)

Expanded stale notice details:

![Expanded stale notice
details](docs/pr-screenshots/pr-5356/issue-thread-notices-expanded.png)

## Risks

- Moderate risk: this touches issue activity serialization and
issue-thread rendering, both of which are central operator surfaces.
- Migration risk is low: the only migration change makes an existing
migration idempotent.
- No new migrations are introduced, so there is no cross-PR migration
ordering requirement.

> 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 coding agent, shell/tool-use enabled, used to
split the existing branch, verify the isolated PR branch, and create
this PR.

## 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>

packages/shared/src/types/issue.ts

@@ -434,6 +434,7 @@ export interface IssueCommentMetadataSection {
 
 export interface IssueCommentMetadata {
   version: 1;
+  sourceRunId?: string | null;
   sections: IssueCommentMetadataSection[];
 }
 

packages/shared/src/validators/issue.test.ts

@@ -65,6 +65,7 @@ describe("issue validators", () => {
       },
       metadata: {
         version: 1,
+        sourceRunId: "11111111-1111-4111-8111-111111111111",
         sections: [
           {
             title: "Evidence",
@@ -79,6 +80,7 @@ describe("issue validators", () => {
     });
 
     expect(parsed.presentation?.detailsDefaultOpen).toBe(false);
+    expect(parsed.metadata?.sourceRunId).toBe("11111111-1111-4111-8111-111111111111");
     expect(parsed.metadata?.sections[0]?.rows).toHaveLength(3);
   });
 

packages/shared/src/validators/issue.ts

@@ -318,6 +318,7 @@ export const issueCommentMetadataSectionSchema = z.object({
 
 export const issueCommentMetadataSchema = z.object({
   version: z.literal(1),
+  sourceRunId: z.string().uuid().nullable().optional(),
   sections: z.array(issueCommentMetadataSectionSchema).min(1).max(20),
 }).strict();