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>

server/src/__tests__/issue-activity-events-routes.test.ts

@@ -1,5 +1,6 @@
 import express from "express";
 import request from "supertest";
+import { getTableName } from "drizzle-orm";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import { normalizeIssueExecutionPolicy } from "../services/issue-execution-policy.ts";
 
@@ -266,6 +267,76 @@ describe("issue activity event routes", () => {
     });
   }, 15_000);
 
+  it("logs readable workspace change activity details for issue updates", async () => {
+    const previousProjectWorkspaceId = "aaaaaaaa-aaaa-4aaa-8aaa-aaaaaaaaaaaa";
+    const nextExecutionWorkspaceId = "bbbbbbbb-bbbb-4bbb-8bbb-bbbbbbbbbbbb";
+    const issue = {
+      ...makeIssue(),
+      projectId: "cccccccc-cccc-4ccc-8ccc-cccccccccccc",
+      projectWorkspaceId: previousProjectWorkspaceId,
+      executionWorkspaceId: null,
+      executionWorkspacePreference: "shared_workspace",
+      executionWorkspaceSettings: { mode: "shared_workspace" },
+    };
+    mockIssueService.getById.mockResolvedValue(issue);
+    mockIssueService.update.mockImplementation(async (_id: string, patch: Record<string, unknown>) => ({
+      ...issue,
+      ...patch,
+      updatedAt: new Date(),
+    }));
+
+    const dbMock = {
+      select: vi.fn(() => ({
+        from: (table: unknown) => ({
+          where: async () => {
+            const tableName = getTableName(table as Parameters<typeof getTableName>[0]);
+            if (tableName === "project_workspaces") {
+              return [{ id: previousProjectWorkspaceId, name: "Main workspace" }];
+            }
+            if (tableName === "execution_workspaces") {
+              return [{ id: nextExecutionWorkspaceId, name: "Feature workspace" }];
+            }
+            return [];
+          },
+        }),
+      })),
+    };
+
+    const res = await request(await createApp(dbMock))
+      .patch(`/api/issues/${issue.id}`)
+      .send({ executionWorkspaceId: nextExecutionWorkspaceId });
+
+    expect(res.status).toBe(200);
+    await vi.waitFor(() => {
+      expect(mockLogActivity).toHaveBeenCalledWith(
+        expect.anything(),
+        expect.objectContaining({
+          action: "issue.updated",
+          details: expect.objectContaining({
+            executionWorkspaceId: nextExecutionWorkspaceId,
+            workspaceChange: {
+              from: {
+                label: "Main workspace",
+                projectWorkspaceId: previousProjectWorkspaceId,
+                executionWorkspaceId: null,
+                mode: "shared_workspace",
+              },
+              to: {
+                label: "Feature workspace",
+                projectWorkspaceId: previousProjectWorkspaceId,
+                executionWorkspaceId: nextExecutionWorkspaceId,
+                mode: "shared_workspace",
+              },
+            },
+            _previous: expect.objectContaining({
+              executionWorkspaceId: null,
+            }),
+          }),
+        }),
+      );
+    });
+  });
+
   it("logs successful_run_handoff_resolved when an in_progress issue transitions to done with a pending required handoff", async () => {
     const issue = { ...makeIssue(), status: "in_progress" };
     mockIssueService.getById.mockResolvedValue(issue);