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/session-manager/save-entry.test.ts

@@ -42,7 +42,7 @@ describe("SessionManager.saveCustomEntry", () => {
 		expect(customEntry.parentId).toBe(msgId);
 
 		// Tree structure should be correct
-		const path = session.getPath();
+		const path = session.getBranch();
 		expect(path).toHaveLength(3);
 		expect(path[0].id).toBe(msgId);
 		expect(path[1].id).toBe(customId);