Rework custom tools API with CustomToolContext

- CustomAgentTool renamed to CustomTool
- ToolAPI renamed to CustomToolAPI
- ToolContext renamed to CustomToolContext
- ToolSessionEvent renamed to CustomToolSessionEvent
- Added CustomToolContext parameter to execute() and onSession()
- CustomToolFactory now returns CustomTool<any, any> for type compatibility
- dispose() replaced with onSession({ reason: 'shutdown' })
- Added wrapCustomTool() to convert CustomTool to AgentTool
- Session exposes setToolUIContext() instead of leaking internals
- Fix ToolExecutionComponent to sync with toolOutputExpanded state
- Update all custom tool examples for new API

packages/coding-agent/test/compaction-hooks.test.ts

@@ -99,16 +99,19 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 		const modelRegistry = new ModelRegistry(authStorage);
 
 		hookRunner = new HookRunner(hooks, tempDir, sessionManager, modelRegistry);
-		hookRunner.setUIContext(
-			{
+		hookRunner.initialize({
+			getModel: () => session.model,
+			sendMessageHandler: async () => {},
+			appendEntryHandler: async () => {},
+			uiContext: {
 				select: async () => undefined,
 				confirm: async () => false,
 				input: async () => undefined,
 				notify: () => {},
 				custom: () => ({ close: () => {}, requestRender: () => {} }),
 			},
-			false,
-		);
+			hasUI: false,
+		});
 
 		session = new AgentSession({
 			agent,