fix: add blockedMessage to guard result, emit header in screenshot fallback

- Add blockedMessage string to GuardResult so all 10 UI automation
  tools can correctly check and emit the guard message via statusLine
- Emit headerEvent and statusLine in the screenshot optimization-failure
  base64 path for consistent client responses

Author: cameroncooke

src/mcp/tools/ui-automation/screenshot.ts

@@ -276,6 +276,11 @@ export async function screenshotLogic(
             log('warn', `${LOG_PREFIX}/screenshot: Failed to delete temp file: ${err}`);
           }
 
+          ctx.emit(headerEvent);
+          ctx.emit(statusLine('success', 'Screenshot captured'));
+          ctx.emit(
+            detailTree([{ label: 'Format', value: 'image/png (optimization failed)' }]),
+          );
           ctx.attach({ data: base64Image, mimeType: 'image/png' });
           return;
         }

src/utils/debugger/ui-automation-guard.ts

@@ -7,6 +7,7 @@ import type { DebuggerManager } from './debugger-manager.ts';
 
 type GuardResult = {
   blockedResponse?: ToolResponse;
+  blockedMessage?: string;
   warningText?: string;
 };
 
@@ -55,6 +56,7 @@ export async function guardUiAutomationAgainstStoppedDebugger(opts: {
       'UI automation blocked: app is paused in debugger',
       details,
     ),
+    blockedMessage: `UI automation blocked: app is paused in debugger\n${details}`,
   };
 }