feat(runtime-host): broker nested capability forms

Route Client Capability interaction requests through the Runtime-owned form callback. Pause provider execution time only while the canonical form is pending, bound result delivery, and rearm a fresh execution timeout after delivery.\n\nClose the exact producer-owned form before settling provider failure, cancellation, or connection loss, while preserving Runtime Host as the only Interaction authority.\n\nPart of #4364.\n\nGenerated-by: OpenAI Codex

Author: me2seeks

apps/desktop/src/main/__tests__/runtime-host-desktop-candidate.test.ts

@@ -1207,6 +1207,7 @@ function connectionHarness(
       return provider.call(frame, {
         signal: new AbortController().signal,
         accept: async () => undefined,
+        requestInteraction: async () => assert.fail('Unexpected provider interaction'),
       });
     },
     disconnect: () => resolveClosed?.(),

apps/desktop/src/main/__tests__/runtime-host-native-capabilities.test.ts

@@ -528,6 +528,7 @@ test('forwards Host cancellation to an admitted Desktop invocation', async () =>
   const inFlight = provider.call(capabilityFrame(), {
     signal: controller.signal,
     accept: async () => undefined,
+    requestInteraction: async () => assert.fail('Unexpected provider interaction'),
   });
 
   await started;
@@ -649,5 +650,6 @@ async function call(
   return provider.call(frame, {
     signal: new AbortController().signal,
     accept: async () => accept(),
+    requestInteraction: async () => assert.fail('Unexpected provider interaction'),
   });
 }

packages/cli/src/__tests__/runtime-host-capability-provider-command.test.ts

@@ -87,6 +87,7 @@ test('MCP capability publication freezes an accepted callable tool snapshot', as
       accept: async () => {
         accepted = true;
       },
+      requestInteraction: async () => assert.fail('Unexpected provider interaction'),
     },
   );
   assert.deepEqual(result, { content: [{ type: 'text', text: '{"path":"README.md"}' }] });