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/src/modes/rpc/rpc-mode.ts

@@ -15,7 +15,7 @@ import * as crypto from "node:crypto";
 import * as readline from "readline";
 import type { AgentSession } from "../../core/agent-session.js";
 import type { ExtensionUIContext, ExtensionUIDialogOptions } from "../../core/extensions/index.js";
-import { theme } from "../interactive/theme/theme.js";
+import { type Theme, theme } from "../interactive/theme/theme.js";
 import type {
 	RpcCommand,
 	RpcExtensionUIRequest,
@@ -229,6 +229,19 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
 		get theme() {
 			return theme;
 		},
+
+		getAllThemes() {
+			return [];
+		},
+
+		getTheme(_name: string) {
+			return undefined;
+		},
+
+		setTheme(_theme: string | Theme) {
+			// Theme switching not supported in RPC mode
+			return { success: false, error: "Theme switching not supported in RPC mode" };
+		},
 	});
 
 	// Set up extensions with RPC-based UI context