Chat: one phone header button, quick-prompt chips, double-click to reuse a message

The phone header carries a single speech bubble: Control on Home, the
assistant elsewhere. Chips above the input offer the user's most sent
messages per tab, then starters; a tap or a double-click on a sent or
heard message fills the input without sending.

docs/code/agents.md

@@ -65,6 +65,11 @@ yours.
 `MCP_ENABLED` is only needed for external clients, so the built-in assistant
 works without it.
 
+In both tabs, chips above the input offer quick prompts: the messages you send
+most often in this browser, then a few starters. A tap puts the text in the
+input to edit and send. Double-clicking, or double-tapping, one of your own
+messages does the same.
+
 ## Control
 
 A live [Wren](../reference/node-types.md#wren) or