feat: improve session naming, project display, rename support, tab titles

Backend:
- sessions.py: include workspace_name in session response
- instance_service.py: auto-generate display names as
  'Project / Workspace / Tool #N' instead of 'Workspace / Tool #N'
- instance_service.py: add rename_tool_instance() service function
- tool_instances.py: add PATCH /instances/{id} endpoint for renaming
  display_name

Frontend:
- api/sessions.ts: add workspace_name to Session type, add renameInstance()
- use-instance-actions.ts: add handleRename, set document.title when opening
- session-card.tsx: click-to-edit display_name inline; always show project
  context line (Project / Workspace or Repo / Tool)
- session-list.tsx: pass through onRename prop
- SessionsPage.tsx: wire handleRename to SessionCard and SessionList
- app-shell.tsx: sidebar tooltip includes workspace or repo name
- use-terminal-page.ts: set document.title based on active terminal session

Quality gates: py_compile all backend files pass, tsc --noEmit pass,
npm run build pass, 82/82 tests pass

apps/web/src/styles/pages/sessions.css

@@ -1,3 +1,26 @@
+/* Session card rename */
+.session-card-rename input {
+	font: inherit;
+	font-weight: 600;
+	font-size: 1rem;
+	padding: 0.25rem 0.5rem;
+	border: 1px solid var(--border);
+	border-radius: 0.375rem;
+	background: var(--surface);
+	color: var(--text);
+	width: 100%;
+	min-width: 0;
+}
+
+.session-card-context {
+	font-size: 0.8125rem;
+	margin-top: 0.25rem;
+}
+
+.session-card-context strong {
+	color: var(--text);
+}
+
 /* Mobile Sessions Page */
 @media (max-width: 767px) {
 	.sessions-page {