feat: CLI session bridge - read CLI sessions from agent SQLite store

Read CLI sessions from the agent's state.db and surface them in the
WebUI sidebar alongside local sessions, with read-only display and
import-on-click to avoid data duplication.

Key changes:
- get_cli_sessions(): reads sessions list via parameterized SQL,
  wrapped in sqlite3 context manager (no connection leaks)
- get_cli_session_messages(): reads messages for a CLI session
  via parameterized SQL, also context-managed
- GET /api/sessions: merges WebUI + CLI sessions with dedup
  (WebUI takes priority on same session_id)
- GET /api/session: falls back to CLI store if not a WebUI session
- POST /api/session/import_cli: imports a CLI session into the
  WebUI store (idempotent, no duplicates on re-import)
- Imported sessions use get_last_workspace() for the workspace field
  (not a hardcoded string) and carry the active profile tag
- CSS: .cli-session with ::after 'cli' indicator (no theme changes)

Fixes review feedback:
- SQLite connections use 'with' context managers (no leaks)
- Workspace uses real path via get_last_workspace()
- Profile awareness via api.profiles.get_active_profile_name()
- Parameterized SQL queries throughout (no injection risk)
- Graceful fallback when sqlite3 or state.db is missing

static/style.css

@@ -688,3 +688,19 @@ body.resizing{user-select:none;cursor:col-resize;}
 .thinking-card-body pre{font-family:'SF Mono',ui-monospace,monospace;font-size:11px;line-height:1.5;color:var(--muted);white-space:pre-wrap;word-break:break-word;margin:0;}
 
 .bg-error-banner{background:rgba(229,62,62,.15);border:1px solid rgba(229,62,62,.3);color:#fca5a5;padding:8px 16px;font-size:12px;display:flex;align-items:center;justify-content:space-between;gap:12px;border-radius:0;}
+
+/* ── CLI session items in sidebar ── */
+.session-item.cli-session {
+  border-left-color: var(--gold);
+}
+.session-item.cli-session::after {
+  content: 'cli';
+  font-size: 9px;
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: .04em;
+  color: var(--gold);
+  opacity: .5;
+  margin-left: 4px;
+  flex-shrink: 0;
+}