fix: restore pending edits before apply

[GTC2080]

Summary

• Restore saved pending edit queues when /apply or /discard runs with an empty in-memory queue.
• Keep review-mode queued edits recoverable after a session restart or delayed mount hydration.

Validation

• npm test -- tests/use-code-mode-pending-apply.test.tsx tests/pending-edits.test.ts tests/slash.test.ts tests/review-edit-gate.test.ts
• npx biome check src/cli/ui/hooks/useCodeMode.ts tests/use-code-mode-pending-apply.test.tsx
• npm run typecheck
• npm run verify

Review Evidence

• Linked issue: Fixes 改动项排队确认，无法/apply 确认改动 #2256
• Screenshots: not applicable, no visual UI/layout change.
• Performance data: not applicable, no cache, token, or runtime performance behavior change.

Fixes #2256