feat: add workflow dry-run observability

agent-run-gateway.test.mjs

@@ -443,6 +443,20 @@ test('shadow observer failure cannot fail a Native run and chat runs are not obs
       observations += 1;
       const error = new Error('shadow unavailable');
       error.code = 'SHADOW_UNAVAILABLE';
+      error.mode = 'shadow';
+      error.executionPlan = {
+        version: 'workflow-execution-decision-v1',
+        candidateEngine: 'native',
+        effectiveEngine: 'native',
+        fallbackEngine: 'native',
+        reason: 'shadow',
+        candidateReason: 'canary_not_selected',
+        configVersion: 10,
+        bucket: 91,
+        taskType: 'code_task',
+        dryRun: true,
+        handoffAllowed: false,
+      };
       throw error;
     },
   });
@@ -466,6 +480,8 @@ test('shadow observer failure cannot fail a Native run and chat runs are not obs
   assert.equal(observations, 1);
   const failure = pool.events.find((event) => event.eventType === 'workflow_shadow_failed');
   assert.equal(JSON.parse(failure.dataJson).code, 'SHADOW_UNAVAILABLE');
+  const plan = pool.events.find((event) => event.eventType === 'workflow_execution_planned');
+  assert.equal(JSON.parse(plan.dataJson).candidateReason, 'canary_not_selected');
 });
 
 test('canary dry-run records the candidate decision without changing Native run state', async () => {
@@ -487,6 +503,7 @@ test('canary dry-run records the candidate decision without changing Native run
         candidateReason: 'percentage',
         configVersion: 9,
         bucket: 3,
+        taskType: 'repo_refactor',
         dryRun: true,
         handoffAllowed: false,
       },
@@ -520,6 +537,7 @@ test('canary dry-run records the candidate decision without changing Native run
     candidateReason: 'percentage',
     configVersion: 9,
     bucket: 3,
+    taskType: 'repo_refactor',
     dryRun: true,
     handoffAllowed: false,
   });