feat: multi-session terminal frontend UI + tests (PR 3)

- Add TerminalSessionTabs component with status dots, rename, close, max-5 limit
- Add 7 component tests for tab rendering, selection, close, rename
- TerminalComponent: sessionId prop, forwardRef with fit() method
- TerminalPage: multi-session orchestration, tab switching, auto-create default
- Fullscreen mode: Alt+Shift+F toggle, auto-hide tabs, Esc exit
- Keyboard shortcuts: Alt+Shift+N/W/ArrowLeft/ArrowRight/R
- Add CSS for tabs, fullscreen, mobile responsive
- Update useTerminalSessions hook for session CRUD
- terminal_manager.py: lookup by internal session_id fallback

Quality gates: tsc --noEmit clean, vitest (7/7 new tests passed), pytest (182 passed)

apps/api/src/services/terminal_manager.py

@@ -248,8 +248,26 @@ class TerminalManager:
         instance_id: str,
         session_id: str,
     ) -> TerminalSession | None:
-        """Lookup a session by composite key."""
-        return self._sessions.get((instance_id, session_id))
+        """Lookup a session by composite key, or by internal session_id."""
+        session = self._sessions.get((instance_id, session_id))
+        if session is not None:
+            return session
+        # Fallback: search by internal TerminalSession.session_id
+        for (iid, _sid), sess in self._sessions.items():
+            if iid == instance_id and sess.session_id == session_id:
+                return sess
+        return None
+
+    def _find_key_by_internal_id(
+        self,
+        instance_id: str,
+        internal_session_id: str,
+    ) -> tuple[str, str] | None:
+        """Find the manager dict key for a session by its internal session_id."""
+        for (iid, sid), session in self._sessions.items():
+            if iid == instance_id and session.session_id == internal_session_id:
+                return (iid, sid)
+        return None
 
     def get_sessions_for_instance(
         self,
@@ -328,6 +346,7 @@ class TerminalManager:
         container_id: str,
         startup_command: str | None = None,
         session_id: str | None = None,
+        name: str | None = None,
     ) -> TerminalSession:
         """Reset a session by killing it and creating a new one.
 
@@ -336,6 +355,7 @@ class TerminalManager:
             container_id: Docker container ID.
             startup_command: Optional startup command.
             session_id: Specific session to reset. If None, resets the default session.
+            name: Optional name to preserve for the new session.
 
         Returns:
             The newly created TerminalSession.
@@ -344,6 +364,11 @@ class TerminalManager:
         target_session_id = session_id or "default"
         key = (instance_id_str, target_session_id)
 
+        # Preserve old name if not provided
+        old_name = name
+        if old_name is None and key in self._sessions:
+            old_name = self._sessions[key].name
+
         # Close existing session if any
         if key in self._sessions:
             logger.debug(
@@ -363,7 +388,7 @@ class TerminalManager:
             instance_id=instance_id,
             container_id=container_id,
             startup_command=startup_command,
-            name="Session 1" if target_session_id == "default" else None,
+            name=old_name or ("Session 1" if target_session_id == "default" else None),
         )
         await new_session.start(startup_command=startup_command)
         self._sessions[key] = new_session