Goal

Make the session/directory lifecycle explicit after #436, so PawWork no longer relies on provider remounts, stale route snapshots, or scattered readiness booleans to keep session UI and execution actions correct.

When this task is done:

• Timeline rendering is keyed by a durable session identity.
• Execution actions are keyed by an explicit current execution directory/scope.
• Follow-up, revert, slash-command parsing, model selection, review, and VCS actions all use the same readiness/scope model or clearly document why they do not.
• Async results from stale execution contexts cannot write into the current UI/store state.
• The original [Bug] exit-worktree triggers full session view teardown/rebuild, causing timeline flash, layout shift, and scroll-to-top #432 long-timeline path has a stable verification path.

Scope

In scope:

• Define SessionScope, likely { serverKey, sessionID }.
• Define ExecutionScope, likely { directory, client, store, setStore, epoch }.
• Keep timeline rendering keyed by SessionScope.
• Keep execution actions keyed by ExecutionScope.
• Replace scattered action gates with one observable action-readiness selector, with components such as cacheReady, statusReady, commandsReady, providerReady, and localModelReady.
• Block /custom-command submit until command hydration is ready.
• Block or defer sends until directory-local model selection hydration is ready.
• Move follow-up persistence and queued draft ownership to { serverKey, sessionID } or an equivalent collision-proof scope.
• Persist source scope with queued follow-up drafts and verify it before auto-send.
• Add epoch/revision guards for async revert/restore, prompt rollback, VCS/review, and artifact result application.
• Add a stable e2e, browser-level, or diagnostics-backed regression for enter-worktree -> exit-worktree -> follow-up on a long session.
• Clean up duplicate or misleading readiness/state names such as session_status_ready, session_status_state, statusKnown, and routeReady where practical.

Already handled in #436, do not duplicate unless a regression appears:

• Same-session activeDirectory changes do not unmount MessageTimeline.
• Last-good timeline messages survive transient same-session cache misses.
• Follow-up, revert, and review helpers no longer use initial directory/client snapshots.
• Review VCS diff tasks/results are guarded by execution directory.
• session.status() hydration preserves active events that arrive during the request and clears stale pre-request busy / retry when the fresh snapshot is idle.
• Current-directory child-store retention follows the live directory accessor instead of a long-lived provider owner.

Out of scope:

• Reintroducing timeline remounts on activeDirectory changes.
• Using scroll repair as the primary fix for [Bug] exit-worktree triggers full session view teardown/rebuild, causing timeline flash, layout shift, and scroll-to-top #432.
• Migrating every sync cache and persistence bucket in one unreviewable change.
• Mixing this Stage 2 architecture work into fix(app): keep session timeline stable across worktree exit #436 unless it fixes a concrete regression found before merge.

Relevant files or context

Related issues and PRs:

• [Bug] exit-worktree triggers full session view teardown/rebuild, causing timeline flash, layout shift, and scroll-to-top #432: original exit-worktree timeline stability issue.
• fix(app): keep session timeline stable across worktree exit #436: Stage 1 stopgap PR.
• [Task] Stage 2: separate session identity from execution directory #441: this Stage 2 tracking issue.

Likely files and areas:

• packages/app/src/context/sync.tsx
• packages/app/src/context/global-sync.tsx
• packages/app/src/context/global-sync/bootstrap.ts
• packages/app/src/context/global-sync/child-store.ts
• packages/app/src/context/local.tsx
• packages/app/src/pages/session.tsx
• packages/app/src/pages/session/use-session-followups.ts
• packages/app/src/pages/session/use-session-revert.ts
• packages/app/src/pages/session/use-session-review-state.ts
• packages/app/src/pages/session/use-session-timeline-data.ts
• packages/app/src/components/prompt-input.tsx
• packages/app/src/components/prompt-input/submit.ts

Important review context from #436:

• Same sessionID under different server/workspace must not reuse timeline, follow-up, or action state accidentally.
• Directory switch followed by immediate /custom-command must not send command text as a normal prompt before command.list hydrates.
• Directory switch followed by immediate send must not use fallback model/provider while local persisted model selection is still hydrating.
• Click revert, switch directory before the request settles, and verify API client, store writes, and prompt rollback only affect the click-time execution scope.
• Old async results must not overwrite a newer execution context even if the directory string is reused.

Verification

Required checks for the closing PR:

• Add focused unit tests for SessionScope and ExecutionScope behavior.
• Add action-readiness tests covering command hydration, provider/model hydration, session cache readiness, and status readiness.
• Add follow-up queue tests proving two servers/workspaces with the same sessionID do not share queued drafts.
• Add async stale-result tests for revert/restore, prompt rollback, and VCS/review result application.
• Add a stable regression for the original long-timeline path: enter-worktree -> exit-worktree -> follow-up.
• Verify MessageTimeline does not unmount, rendered count does not reset to the initial small window, scrollTop does not jump near 0, and follow-up sends against the intended execution directory.
• Run the relevant focused app tests.
• Run bun --cwd packages/app run typecheck.
• Run bun --cwd packages/app run test:unit unless the closing PR gives a concrete reason to use a narrower suite.
• Run git diff --check.

Execution mode

Agent should investigate and propose a plan first.