refactor(coding-agent): unify tool and event handler context creation

Tools now use ExtensionRunner.createContext() instead of a separate
inline context factory. This ensures tools and event handlers share
the same context, fixing ctx.shutdown() and other context methods.

- Made ExtensionRunner.createContext() public
- Changed wrapRegisteredTools to accept ExtensionRunner instead of getContext callback
- Create ExtensionRunner when SDK custom tools are present (not just extensions)
- Removed redundant inline context factory from sdk.ts

packages/coding-agent/src/core/extensions/runner.ts

@@ -296,7 +296,11 @@ export class ExtensionRunner {
 		this.shutdownHandler();
 	}
 
-	private createContext(): ExtensionContext {
+	/**
+	 * Create an ExtensionContext for use in event handlers and tool execution.
+	 * Context values are resolved at call time, so changes via initialize() are reflected.
+	 */
+	createContext(): ExtensionContext {
 		return {
 			ui: this.uiContext,
 			hasUI: this.hasUI(),