test: E2E for Conductor prose + fix auto-decide-preserved GSTACK_HOME bug

- New skill-e2e-conductor-prose (periodic): Conductor env + plan-eng-review
  surfaces a prose decision brief, not a silent skip. Header documents this is
  end-to-end behavior coverage; the deterministic Conductor guard is the
  question-preference-hook unit test (the PTY harness can't register the MCP
  variant — Codex #10).
- Fix the pre-existing bug in auto-decide-preserved: it seeded the never-ask
  preference under GSTACK_HOME=tmpHome but never passed GSTACK_HOME into the
  PTY run, so the spawned claude read the real ~/.gstack and the preference
  was inert (Codex #9). Now passes GSTACK_HOME + CONDUCTOR_WORKSPACE_PATH to
  prove auto-decide still wins over the Conductor prose redirect.
- Register both in touchfiles (periodic tier).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/skill-e2e-conductor-prose.test.ts

@@ -0,0 +1,69 @@
+/**
+ * Conductor → prose decision brief (periodic-tier, paid, real-PTY).
+ *
+ * Proves the end-to-end behavior: when CONDUCTOR_SESSION is signalled, a skill
+ * that hits a decision renders a PROSE decision brief and waits, instead of
+ * silently skipping the user.
+ *
+ * SCOPE — read before trusting this as the Conductor guard. This is END-TO-END
+ * BEHAVIOR coverage, NOT the discriminating Conductor guarantee:
+ *   - The deterministic guard is test/question-preference-hook.test.ts
+ *     ("Conductor prose redirect") — it sets process.env.CONDUCTOR_* and asserts
+ *     the PreToolUse hook denies + redirects. That test CAN fail on unfixed code.
+ *   - The PTY harness here cannot register `mcp__conductor__AskUserQuestion`, so
+ *     it tests "native AUQ unavailable + Conductor signal → prose," NOT "the MCP
+ *     variant exists and must not be called" (Codex #10). Under --disallowedTools
+ *     a present-human interactive session already prose-falls-back, so this test
+ *     is a smoke check that the Conductor path still produces a prose brief, not
+ *     a proof that the Conductor signal (vs the generic fallback) drove it.
+ *
+ * Periodic tier: model-behavior, non-deterministic.
+ */
+
+import { describe, test, expect } from 'bun:test';
+import { runPlanSkillObservation } from './helpers/claude-pty-runner';
+
+const shouldRun = !!process.env.EVALS && process.env.EVALS_TIER === 'periodic';
+const describeE2E = shouldRun ? describe : describe.skip;
+
+const FLAWED_PLAN = `# Plan: add a "developer-friendly" pricing tier
+
+## Goal
+Increase developer adoption.
+
+## Premise
+No tests mentioned, no rollout plan, no auth check on the upgrade endpoint.
+Adds a Stripe tier, a React pricing page, a Postgres entitlements table, and a
+Redis cache. The team "feels like" it should be cheaper; no developer was asked.
+`;
+
+describeE2E('Conductor renders decisions as prose (periodic)', () => {
+  test('plan-eng-review in a Conductor session surfaces a PROSE decision brief, not a silent skip', async () => {
+    const obs = await runPlanSkillObservation({
+      skillName: 'plan-eng-review',
+      inPlanMode: true,
+      // Mimic Conductor: native AUQ disabled + the Conductor env signal present.
+      extraArgs: ['--disallowedTools', 'AskUserQuestion'],
+      env: { CONDUCTOR_WORKSPACE_PATH: '/tmp/conductor-prose-e2e' },
+      initialPlanContent: FLAWED_PLAN,
+      timeoutMs: 300_000,
+    });
+
+    // The decision must reach the human as prose. 'silent_write' (wrote findings
+    // to the plan without asking) is the precise failure we guard against.
+    if (obs.outcome === 'silent_write') {
+      throw new Error(
+        `Conductor prose regression: skill wrote findings without surfacing a decision.\n` +
+          `summary: ${obs.summary}\n--- evidence ---\n${obs.evidence}`,
+      );
+    }
+    if (obs.outcome === 'exited' || obs.outcome === 'timeout') {
+      throw new Error(
+        `Conductor prose test inconclusive: outcome=${obs.outcome}\n` +
+          `summary: ${obs.summary}\n--- evidence ---\n${obs.evidence}`,
+      );
+    }
+    // A prose-rendered decision brief was observed at some point in the run.
+    expect(obs.proseAUQEverObserved).toBe(true);
+  }, 360_000);
+});