Unify TUI runtime commands with gateway and harden gateway restart

docs/architecture/AGENT_DIAGRAM.md

@@ -100,6 +100,7 @@ ChannelAdapter  ->  ChannelRegistry
         |               |
         |               +----> Runtime backend mode overrides
         |                      (/runtime status|activate pi|deactivate pi|use config)
+        |                      (TUI `/runtime` is forwarded via gateway/daemon command path)
         |               |
         |               v
         |         SessionManager

docs/architecture/GATEWAY_SESSIONS_AND_QUEUE.md

@@ -12,6 +12,7 @@ If you only want the protocol surface, see `docs/api/PROTOCOL.md`.
 - Sessions persist in SQLite via `SessionManager` even if clients disconnect.
 - Once dequeued, message routing may execute the native orchestrator path or an optional external backend path (`claude_code`, `opencode`, `codex`, `gemini`, `pi_embedded`) depending on agent/backend config.
 - Runtime backend mode can be overridden manually via `/runtime` command fast-path (`status`, `activate pi`, `deactivate pi`, `use config`) and is persisted in preferences (`/backend` remains a compatibility alias).
+- `flynn tui` now attaches to this same gateway command path for `/runtime ...` and auto-starts/attaches daemon+gateway when needed.
 - Backend routing outcomes are auditable via `backend.route` / `backend.success` / `backend.fallback`, which enables offline canary evaluation without changing gateway protocol methods.
 
 ## Component Map
@@ -24,6 +25,7 @@ flowchart LR
   end
 
   subgraph GW[Gateway Process]
+    TUI[TUI client\n(runtime command forwarding)]
     WS[WebSocket connection\n(connectionId)]
     GS[GatewayServer]
     LQ[LaneQueue\nper-session FIFO]
@@ -37,6 +39,7 @@ flowchart LR
     AO[AgentOrchestrator / External Backends]
   end
 
+  TUI --> WS
   WS --> GS
   QP --> GS
   BM --> GS