feat: implement tool-session progress panel and live list updates

- Add SessionOperationsContext + SessionProgressPanel for global,
  non-blocking lifecycle progress (create/start/stop/restart/delete/
  recreate-tunnel) driven by SSE events.
- Promote SessionsContext to authoritative shared session state with
  refresh, addOrUpdateSession, and removeSession helpers.
- Wire AppShell, DashboardPage, SessionsPage, useInstanceActions,
  ToolStarter, and InstanceList into shared state so lists update
  immediately after create/delete without manual refresh.
- Remove legacy blocking overlays from CreateSessionForm, SessionCard,
  and InstanceList; keep disabled states and inline spinners only.
- Update DashboardPage tests to wrap with SessionsProvider and
  SessionOperationsProvider.
- Add .cache/ to .gitignore.

Quality gates: npm run typecheck, npm run lint, npm test -- --run
(82 passed).

openspec/changes/tool-session-progress-and-updates/design.md

@@ -0,0 +1,71 @@
+# Design: Tool Session Progress and Live Updates
+
+## Goals / Non-Goals
+
+**Goals:**
+- Provide structured, real-time progress feedback for every tool lifecycle action.
+- Ensure all session lists (nav, dashboard, sessions page) update immediately after create/delete.
+- Remove blocking and card-dimming overlays that hide context and provide no step detail.
+- Keep the change frontend-only, reusing existing SSE and session APIs.
+
+**Non-Goals:**
+- No new backend endpoints or event types.
+- No changes to the actual Docker/container orchestration logic.
+- No redesign of the session card layout beyond action/progress affordances.
+
+## Decisions
+
+### Decision: Global progress panel in the corner
+A fixed panel (bottom-right desktop, bottom sheet style on mobile) lists in-flight operations. Each operation shows:
+- Action icon + session display name
+- Current step label derived from the latest SSE event
+- A compact stepper: Created → Building → Starting → Probing → Ready/Error
+- Dismiss button once settled
+
+This is non-blocking, works across pages, and does not interfere with the modal create flow.
+
+### Decision: SSE event-driven updates
+The panel subscribes to `useEvents`. When an operation is started we record `instanceId` + `action`. Incoming events that match a tracked instance update the operation's message, status, and step. Events handled:
+- `instance.created`, `instance.started`, `instance.restarted` → advance
+- `instance.health_changed` with `status=running` → complete success
+- `instance.error` → complete error
+- `instance.stopped` → complete for stop action
+- `instance.deleted` → complete for delete action
+
+### Decision: Shared session state
+`SessionsContext` is promoted from a nav-only data holder to the authoritative session list:
+- Holds `sessions`, `isLoading`, `error`, `refreshSessions()`.
+- Provides `addOrUpdateSession`, `removeSession` for optimistic updates.
+- `AppShell`, `DashboardPage`, and `SessionsPage` read from this context instead of fetching independently.
+
+### Decision: Optimistic create/delete updates
+- **Create**: after the API returns a pending instance, add it to shared state and start tracking. Subsequent SSE events update its status.
+- **Delete**: remove from shared state as soon as the API succeeds; the progress panel tracks the action until the `instance.deleted` event confirms it.
+- **Other actions**: keep the existing per-action busy flag on the card for button disabled states, but the panel provides the detailed progress.
+
+### Decision: Remove legacy overlays
+- Delete `loading-overlay` and workflow step markup from `CreateSessionForm`.
+- Remove `session-busy-overlay` and `instance-busy-overlay` (the dimming overlays), but keep button disabled states and small inline spinners.
+
+## Risks / Trade-offs
+
+**Risk: Shared context causes extra re-renders**
+→ Mitigation: context value is memoized; lists use the same data they already fetched.
+
+**Risk: SSE events arriving before operation is tracked**
+→ Mitigation: start tracking before calling the create/start API; for deletes the removal is optimistic and the panel reconciles on the event.
+
+**Risk: Duplicate feedback between panel and toasts**
+→ Mitigation: panel shows in-flight steps; toasts remain for terminal success/error only. Existing `EventToastBridge` logic is left largely unchanged.
+
+## Migration Plan
+
+1. Extend `SessionsContext` with loading/error/refresh/update helpers.
+2. Create `SessionOperationsContext` + `SessionProgressPanel` and render it in `AppShell`.
+3. Update `useInstanceActions` to use shared state and start/stop tracking operations.
+4. Update `ToolStarter`/`StartToolFAB` to add pending sessions and start tracking.
+5. Update `CreateSessionForm` to remove overlay and report status to parent.
+6. Update `InstanceList` to refresh shared state after create/delete.
+7. Update `SessionsPage` and `DashboardPage` to consume shared context.
+8. Remove legacy overlay styles.
+9. Run typecheck, lint, and tests.