Run chats independently

docs/USER_GUIDE.md

@@ -9,6 +9,14 @@ Choose **Add project** to give the coding agent access to a folder. The agent's
 file tools are bounded to that project. Use **File > New Chat** (`⌘N`) to start
 a chat in the active project. Chats are saved after their first message and can
 be renamed, pinned, archived, compacted, rebuilt, or deleted from the sidebar.
+An active chat has a green dot beside its title. You can switch chats or start
+another one while it works; each chat keeps its own transcript, queued prompts,
+tools, approvals, context, and interactive UI state. Model inference shares the
+single loaded runtime so model weights are not duplicated, while independent
+tool work continues concurrently.
+
+Quitting with active chats asks for confirmation. Confirming stops their model
+and tool work; canceling leaves every chat running.
 
 Use **File > Export Chat as Markdown** (`⇧⌘S`) to save the visible conversation,
 including reasoning and tool results. System-only messages are omitted.