feat(tui): add daemon adapter spike

docs/developers/daemon-client-adapters/tui.md

@@ -0,0 +1,96 @@
+# TUI Daemon Adapter Draft
+
+## Goal
+
+Add a flag-gated TUI transport that talks to `qwen serve` through
+`DaemonSessionClient` instead of creating an in-process `Config` + agent
+runtime.
+
+This is a dogfood path for Mode B client migration. It must not replace the
+default TUI path until output sinks, typed daemon events, session-scoped
+permission, and lifecycle diagnostics are stable.
+
+## Proposed Entry Point
+
+```bash
+QWEN_DAEMON_URL=http://127.0.0.1:4170 qwen --experimental-daemon-tui
+```
+
+Optional:
+
+```bash
+QWEN_DAEMON_TOKEN=... QWEN_DAEMON_WORKSPACE=/repo qwen --experimental-daemon-tui
+```
+
+The CLI should refuse this mode unless both are true:
+
+- `QWEN_DAEMON_URL` or `--daemon-url` is set.
+- `GET /capabilities` advertises `session_create`, `session_prompt`, and
+  `session_events`.
+
+## Minimal Flow
+
+1. Create `DaemonClient` with daemon URL and token.
+2. Fetch `/capabilities`.
+3. Create or attach with `DaemonSessionClient.createOrAttach()`.
+4. Subscribe to `session.events()`.
+5. Submit user prompts through `session.prompt()`.
+6. Route cancel through `session.cancel()`.
+7. Route model switch through `session.setModel()`.
+8. Route permission votes through `session.respondToPermission()`.
+
+## Rendering Contract
+
+The first implementation adds `DaemonTuiAdapter`, a locally verifiable reducer
+and transport spike. It maps only these daemon events:
+
+| Daemon event                             | TUI handling                                 |
+| ---------------------------------------- | -------------------------------------------- |
+| `session_update` / `agent_message_chunk` | Append assistant text                        |
+| `session_update` / `agent_thought_chunk` | Append thinking text                         |
+| `session_update` / `tool_call`           | Show tool call lifecycle                     |
+| `permission_request`                     | Show existing confirmation UI where possible |
+| `permission_resolved`                    | Close or update confirmation UI              |
+| `model_switched`                         | Update footer/model display                  |
+| `session_died`                           | Show disconnected state and stop streaming   |
+
+Unknown events must be ignored, not fatal. Typed event reducers will land in a
+later protocol PR.
+
+The adapter is not wired into the default Ink app yet. Existing interactive TUI,
+JSONL, stream-json, and dual-output behavior remains unchanged.
+
+## Explicit Non-Goals
+
+- Do not remove the current TUI in-process runtime.
+- Do not change JSONL, stream-json, or dual-output behavior in this PR.
+- Do not expose file CRUD, MCP management, memory CRUD, or provider/auth
+  mutation through TUI yet.
+- Do not make browser/web direct-to-daemon assumptions; this is terminal only.
+
+## Merge Safety
+
+- Default off.
+- Additive code path.
+- No existing CLI flags change behavior.
+- If the daemon is unavailable, the experimental path fails before starting the
+  TUI and tells the user to run `qwen serve`.
+
+## Validation Plan
+
+- Unit-test event-to-TUI-state mapping with synthetic daemon events.
+- Unit-test prompt, cancel, model switch, and permission vote forwarding.
+- Unit-test flag/env parsing when the feature flag is wired.
+- Smoke-test against a local `qwen serve`:
+  - prompt text streams into the TUI
+  - cancel resolves the active prompt
+  - permission request can be accepted or rejected
+  - reconnect sends the tracked `Last-Event-ID`
+
+## Blockers Before Default Migration
+
+- Typed daemon event schema.
+- Session-scoped permission route.
+- Output sink refactor for JSONL / stream-json / dual-output parity.
+- Session lifecycle close/delete semantics.
+- Runtime diagnostics for MCP, skills, providers, and workspace env.