feat(coding-agent): add user_bash event and theme API extensions

- user_bash event for intercepting ! and !! commands (#528)
- Extensions can return { operations } or { result } to redirect/replace
- executeBashWithOperations() for custom BashOperations execution
- session.recordBashResult() for extensions handling bash themselves
- Theme API: getAllThemes(), getTheme(), setTheme() on ctx.ui
- mac-system-theme.ts example: sync with macOS dark/light mode
- Updated ssh.ts to use user_bash event

packages/coding-agent/examples/extensions/ssh.ts

@@ -199,6 +199,13 @@ export default function (pi: ExtensionAPI) {
 		}
 	});
 
+	// Handle user ! commands via SSH
+	pi.on("user_bash", (_event) => {
+		const ssh = getSsh();
+		if (!ssh) return; // No SSH, use local execution
+		return { operations: createRemoteBashOps(ssh.remote, ssh.remoteCwd, localCwd) };
+	});
+
 	// Replace local cwd with remote cwd in system prompt
 	pi.on("before_agent_start", async (event) => {
 		const ssh = getSsh();