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/specs/session-lifecycle-ux/spec.md

@@ -0,0 +1,44 @@
+## ADDED Requirements
+
+### Requirement: Lifecycle actions show structured progress
+The system SHALL display non-blocking, structured progress feedback for every tool lifecycle action (create, start, stop, restart, delete, recreate tunnel).
+
+#### Scenario: Create a new session
+- **WHEN** the user creates a session
+- **THEN** a global progress indicator appears showing the current backend step
+- **AND** the indicator advances through Created, Building, Starting, Probing, and Running/Error based on SSE events
+
+#### Scenario: Delete a session
+- **WHEN** the user deletes a session
+- **THEN** the session disappears from the current list immediately
+- **AND** the global progress indicator shows "Deleting…" until the backend confirms deletion via SSE or API response
+
+#### Scenario: Stop or restart a session
+- **WHEN** the user stops or restarts a session
+- **THEN** the global progress indicator shows the action in progress
+- **AND** the indicator updates when the backend publishes the corresponding SSE event
+
+### Requirement: Remove blocking progress overlays
+The system SHALL NOT dim the entire form or card with a generic spinner while an action is in progress.
+
+#### Scenario: Create session form submission
+- **WHEN** the create session form is submitted
+- **THEN** form controls are disabled
+- **AND** no full-screen overlay blocks the rest of the application
+- **AND** progress is shown in the global progress panel
+
+#### Scenario: Card action in progress
+- **WHEN** a session card action is triggered
+- **THEN** the relevant button is disabled or shows a small inline spinner
+- **AND** the card itself remains fully visible and interactive for other sessions
+
+## MODIFIED Requirements
+
+### Requirement: Deleted sessions disappear from UI immediately
+**FROM:** The system SHALL update the frontend state immediately after a session is successfully deleted.
+**TO:** The system SHALL remove the session from all visible lists optimistically when the delete API call succeeds, and reconcile via shared state.
+
+#### Scenario: Delete session from any page
+- **WHEN** the user deletes a session
+- **THEN** the session is removed from the nav sidebar, dashboard, and sessions page without a reload
+- **AND** a failure re-adds the session to the list and shows an error