fix(app): ignore stale file tree requests after reset

[Woolgathererer]

Issue for this PR

Closes #47741

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

After a file-tree reset, an old listing could delete a newer pending request, overwrite its file list, or report a stale error. Check that each promise still owns its in-flight entry before applying results, errors, or cleanup.

The production change is three guards in tree-store.ts; there are no API or layout changes.

How did you verify your code works?

• Added four deterministic tests against the real tree store with deferred list responses. Three regression cases failed before the fix; all four now pass.
• File-tree and cache tests: 15 pass across four files (bun test --conditions=solid src/context/file/tree-store.test.ts src/context/file-content-eviction-accounting.test.ts src/components/file-tree.test.ts src/components/file-tree-v2-model.test.ts, from packages/app).
• bun typecheck in packages/app, Prettier, and git diff --check pass.

Screenshots / recordings

No layout change. Verified the request race at the store boundary; no desktop UI recording was captured.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR