fix(tasks): sync cloud-started tasks into local workspace registry

[oliverb123]

Summary

• Tasks started outside the desktop app (web, CLI, another machine — same user) were already returned by the /api/projects/{id}/tasks/ poll, but the sidebar filter in useSidebarData.ts hides any task without a matching local SQLite workspace row, so they never appeared.
• Mirror the API task list into the local workspace registry: when useTasks() yields a new list, create an idempotent mode: "cloud" workspace row for each missing task, then invalidate the workspaces query so the existing filter passes them through. WorkspaceService.doCreateWorkspace already short-circuits when a row exists, and createWorkspaceInput permits empty paths for cloud mode (same shape task-creation.ts uses for pure cloud tasks today).
• Reconciliation runs from MainLayout.tsx where useTasks() already lives; a useRef<Set> prevents duplicate in-flight calls between polls.

Test plan

• pnpm --filter code typecheck passes
• pnpm --filter code test passes (one pre-existing unrelated git integration timeout)
• Manual: start a task via the web app or CLI as the same user, wait <30s, confirm the task appears in the desktop sidebar with the correct title and that clicking it opens TaskDetail without errors
• Restart the app and confirm the cloud workspace row persists (SQLite-backed)
• Spot-check logs for Workspace already exists for task ... on subsequent polls — no duplicate row creation

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
apps/code/src/renderer/components/MainLayout.tsx:110-121
**Workspace query invalidated even when all mutations failed**

`queryClient.invalidateQueries` is called unconditionally in `.then()`, including when every mutation in the batch was rejected. This triggers a workspace refetch even though no new row was written. With React Query's default structural sharing the refetch won't change the `workspaces` reference, so the effect likely won't re-run; but if structural sharing is ever disabled, or tRPC's serialization returns a fresh object, the refetch would bump `workspaces`, re-trigger the effect, and start another mutation batch immediately — bypassing the intended 30-second poll cadence.

### Issue 2 of 2
apps/code/src/renderer/components/MainLayout.tsx:100-110
**`workspaceApi.create` already wraps this call**

`workspaceApi` (exported from `useWorkspace.ts`) exists specifically to provide an imperative surface over `trpcClient.workspace.create.mutate` with the same signature. Using it here would follow the OnceAndOnlyOnce principle and makes it easier to trace the mutation through the codebase.

```suggestion
    void Promise.allSettled(
      missing.map((t) =>
        workspaceApi.create({
          taskId: t.id,
          mainRepoPath: "",
          folderId: "",
          folderPath: "",
          mode: "cloud",
        }),
      ),
    ).then((results) => {
```

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