[Juliusolsson05]

Summary

• add a shared workspace session ownership helper for visible, detached, and buried session owners
• make rehydrate spawn only owned persisted sessions, dropping unowned stale metadata
• make autosave and agent reload prune unowned session rows so stale entries do not survive restarts/reloads
• add a focused assertion test for the ownership invariant

Verification

• npm run test:review-fixes
• npm run test:session-ownership

Notes

• A full npx tsc -b tsconfig.web.json --pretty false still fails on existing repo/submodule/typecheck issues in this fresh worktree, including uninitialized package gitlinks and unrelated renderer diagnostics.
• The codex-headless JSONL tailer follow-up was not included here because packages/codex-headless is a gitlink/submodule in this branch worktree; this PR keeps the main cc-shell workspace-state fix scoped to the parent repo.