Rename session from /resume session list (#863)

* Add session renaming in interactive mode resume picker

Session list now displays last message timestamp as modified time
instead of file mtime. Ctrl+N enters rename mode in the interactive
resume picker, allowing quick session renaming without leaving the
selector. Rename hint is shown only in interactive mode, not in the
CLI --resume picker./

* Add docs entry for renaming in picker

* Update shortcut to ctrl+r for session renaming

packages/coding-agent/src/cli/session-picker.ts

@@ -39,6 +39,7 @@ export async function selectSession(
 				process.exit(0);
 			},
 			() => ui.requestRender(),
+			{ showRenameHint: false },
 		);
 
 		ui.addChild(selector);