Agent chat: pop out into its own window, dock back (#1745)

Thanks @onembyte.

docs/agent-chat.md

@@ -36,6 +36,12 @@ when you send a message or press **Connect**.
   window and let go. The side it would land on lights up while you drag. You can also pick
   **Left** or **Right** under Preferences → AI → Panel. SolidCraft remembers the side.
 - **Width:** drag the panel's inner edge. SolidCraft remembers it.
+- **Its own window:** the pop-out button in the header (a window with an arrow) moves the chat
+  into a window of its own, named after the design, which you can move anywhere, including
+  another screen. The window's own close button closes the chat, which opens there again next
+  time; **Dock** (the same place in its header) puts it back in the side panel. You can also
+  pick **Own window** under Preferences → AI → Panel. SolidCraft remembers where the window
+  was and how big.
 - **Minimise** (the line in the header) folds the panel into a thin strip that keeps the chat
   icon, the agent's state, and a count of anything waiting for your answer. Click the icon to
   unfold it. **Close** (×) hides the panel. Neither stops the agent; **Stop** does.

docs/control-protocol.md

@@ -156,7 +156,7 @@ labels; `prefs:measure_axis_distances` identifies the checkbox.
 | `ui.capture` | `action?`: `capture`, `revert`, `cancel` | answers the Capture Position question (asked when a command starts or the design is saved while components were moved without capturing); without `action`, what waits |
 | `ui.window` | `action`: minimize, maximize, restore, toggle, close | what the title bar's caption buttons do (on Windows and Linux the application bar is the title bar); close asks about unsaved designs first |
 | `ui.agent_cursor` | `show` (bool), `speed`: a number from 1 to 5 (times the normal speed) or `"instant"` (no animation: the command runs at once and the pointer jumps to where it acted), `follow_camera` (bool); all optional | the settings. While the cursor is shown, `engine.execute` first glides to the command's toolbar button and to each pick, then runs and replies; later requests wait their turn. `"animate": false` on a call skips it |
-| `ui.agent_chat` | `features?`, `toolbar_button?`, `permissions?` (`ask`, `edits`, `all`), `add_agent?` ({`name`, `kind`: `acp` or `api`, `command` or `base_url` + `model`}; no keys), `default_agent?`, `agent?` (the conversation's agent, by id), `mode?` (the agent's own mode), `model?` (one of its models), `open?`, `side?` (`left`, `right`), `minimized?`, `width?`, `picker?`, `refresh?`, `connect?`, `stop?`, `send?`: text, `attach_view?`, `permission?`: an option id or `"cancel"` (the newest question of the agent's own), `approve?`: true, false or `"always"` (the oldest request held for Allow/Deny), `cancel?` (Stop: the queue stays), `send_now?` (stop the running step, then send the queued messages), `remove_pending?` (index), `new_chat?` (clear the chat, new session), `undo?` (the last message's changes) | the chat's state: `features`, `agents` (found and added), `currentAgent`, `state` (off, starting, ready, busy, auth, exited), `agent`, `modes`, `mode`, `models`, `model`, `authMethods`, `toolsPort`, `pid`, `waiting`, `turn`, `pending` (queued messages), `stopped`, `detection` and the conversation (`items`). With `features` off only the settings apply. Desktop only; see [Agent chat](agent-chat.md) |
+| `ui.agent_chat` | `features?`, `toolbar_button?`, `permissions?` (`ask`, `edits`, `all`), `add_agent?` ({`name`, `kind`: `acp` or `api`, `command` or `base_url` + `model`}; no keys), `default_agent?`, `agent?` (the conversation's agent, by id), `mode?` (the agent's own mode), `model?` (one of its models), `open?`, `side?` (`left`, `right`), `minimized?`, `popped?` (in its own window), `width?`, `picker?`, `refresh?`, `connect?`, `stop?`, `send?`: text, `attach_view?`, `permission?`: an option id or `"cancel"` (the newest question of the agent's own), `approve?`: true, false or `"always"` (the oldest request held for Allow/Deny), `cancel?` (Stop: the queue stays), `send_now?` (stop the running step, then send the queued messages), `remove_pending?` (index), `new_chat?` (clear the chat, new session), `undo?` (the last message's changes) | the chat's state: `features`, `agents` (found and added), `currentAgent`, `state` (off, starting, ready, busy, auth, exited), `popped`, `window` (its place and size), `agent`, `modes`, `mode`, `models`, `model`, `authMethods`, `toolsPort`, `pid`, `waiting`, `turn`, `pending` (queued messages), `stopped`, `detection` and the conversation (`items`). With `features` off only the settings apply. Desktop only; see [Agent chat](agent-chat.md) |
 | `ui.resize` | `width`, `height` | |
 | `app.quit` | `force?` (quit without asking about unsaved designs) | `quitting` (the window closes), `asking` (a "save changes?" prompt is open) |