Merge branch 'codex/simp-hide-concrete-agent-loop' into codex/simp-hide-subagent-internals

# Conflicts:
#	docs/rfc/implemented/architecture/2026-07-05-prompt-variables-and-tool-guidance-ownership.md
#	packages/subagent/subagent-subprocess/src/index.ts
#	packages/subagent/tool-subagent/src/index.ts

packages/subagent/subagent-inprocess/tests/structured.spec.ts

@@ -37,12 +37,9 @@ const SCHEMA: StructuredOutputSchema = {
 }
 
 /**
- * Real loop + scripted mock model + an INLINE fresh-conversation provider over the
- * shared driver. The concrete backend plugins are deliberately NOT loaded —
- * they would devDep-cycle this package (spawn/fork already depend on the
- * driver), and the runtime under test is the driver's; plugin-level structured
- * coverage lives in the spawn/fork specs. The mock model script drives the
- * child's structured_output calls.
+ * Real loop, scripted model, and inline fresh-conversation provider over the shared driver. Loading
+ * spawn/fork here would create a dev-dependency cycle; their specs cover plugin integration while
+ * this fixture isolates driver behavior and scripts the child's `structured_output` calls.
  */
 async function setup(script: Script, options: SetupOptions = {}) {
   const ctx = new Context()
@@ -217,11 +214,9 @@ describe('in-process structured output', () => {
     ])
     ctx.on('agent/turn-continuation', () => Promise.resolve<ContinuationDecision>({ action: 'stop' }))
     let wrapperInstalled = false
-    // Register before the ready-only start. The child session-start boundary is
-    // after unpublished setup attached structured output but before the loop
-    // can run. The wrapper awaits the
-    // explicit downstream stop above, then overwrites that result with continue.
-    // The later terminal checkpoint still wins.
+    // Register before ready-only start: structured output is attached before session-start and the
+    // loop. The wrapper waits for a downstream stop, rewrites it to continue, and must still lose
+    // to the later terminal checkpoint.
     ctx.on('agent/session-start', (child) => {
       if (child === parent) return
       wrapperInstalled = true
@@ -245,10 +240,8 @@ describe('in-process structured output', () => {
       toolCallResponse('c1', STRUCTURED_OUTPUT_TOOL, { answer: 9 }),
       textResponse('MUST NOT BE CONSUMED'),
     ])
-    // The downstream ordinary policy says stop. A wrapper registered after
-    // start() delegates to that stop, then queues steering; ordinary folding
-    // would turn the stop back into continue. The terminal checkpoint runs
-    // afterwards and discards that steering.
+    // A downstream policy stops, then a later wrapper delegates and queues steering that ordinary
+    // folding would turn into continue. The terminal checkpoint must discard that steering.
     ctx.on('agent/turn-continuation', () => Promise.resolve<ContinuationDecision>({ action: 'stop' }))
     const run = await ctx.subagents.start('spawn', structuredRequest(parent))
     ctx.on('agent/session-start', (child) => {