feat(studio): show staged edit context

[w1ne]

Summary

• Render staged edit source, prompt, target, workflow, and generation id in the review slot.
• Add stale-conflict Rerun prompt recovery that reopens the agent rail without applying stale code.
• Clear stale repair workflow state when rerunning prompt-only staged edits and announce stale warnings.

Test Plan

• npm test -- --run src/studio/tests/StagedEditSlot.test.tsx src/studio/tests/StudioGenerate.test.tsx
• npm run typecheck
• npm run build:studio
• npm run lint
• git diff --check

Review

• Subagent review found stale agentRepairWorkflow contamination on rerun; fixed with a regression assertion.