fix(voyage): S23 — make /trekplan Phase 9 dedup executable (defect #1)

Phase 9's dedup hand-off was broken on two layers, both surfaced by the S22
dogfood: (a) plan-critic + scope-guardian (Read/Glob/Grep, no Write) were told
to write /tmp/*-out.json the dedup helper reads — they cannot; (b) even with
Write, their Output format emits markdown, not the helper's
{agent,findings:[{file,line,rule_key,text}]} schema. readJsonOrNull then
swallowed the absent files -> a silent empty merge that discarded every finding.

Fix (operator-chosen A'): keep the reviewers read-only; make the hand-off run.
- plan-review-dedup.mjs gains a --stdin mode reading {plan_critic,scope_guardian};
  malformed stdin exits non-zero so a broken hand-off surfaces loudly instead of
  collapsing into a silent empty merge. File mode + its tests are untouched.
- plan-critic.md + scope-guardian.md now emit a trailing machine-readable `json`
  findings block (the inline hand-off; no Write tool needed).
- trekplan.md + planning-orchestrator.md Phase 9 rewritten in lockstep: extract
  both blocks, pipe via heredoc into --stdin. No temp files, portable, no
  pathguard dependency.

TDD: malformed-stdin test failed first (CLI ignored stdin -> exit 0 = the bug),
green after impl. New S23 doc-pin asserts both docs use --stdin (not the dead
/tmp paths) and both agents declare the json block. Suite 724 (722/2/0); live
HEAD baseline was 720, not the stale 705 STATE carried forward.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LqBYc8Ltrk7LipyJmGxXiB

tests/lib/doc-consistency.test.mjs

@@ -304,6 +304,37 @@ test('Phase 9 prose mandates parallel single-message dispatch + inline dedup', (
   );
 });
 
+// --- S23 — Phase-9 dedup hand-off is executable (defect #1 fix) ---
+//
+// The read-only reviewers (plan-critic, scope-guardian: Read/Glob/Grep, no Write)
+// cannot write the temp files the old prose told them to. Pin the A′ fix so the
+// broken /tmp-write instruction cannot creep back:
+//   1. Phase-9 prose in BOTH docs must use --stdin, not the dead /tmp/*-out.json
+//      file path the reviewers can't produce.
+//   2. BOTH reviewer agents must declare a machine-readable json findings block
+//      with the keys the dedup helper consumes (agent + findings + rule_key).
+test('S23: Phase-9 dedup hand-off uses --stdin and the reviewers emit a json findings block', () => {
+  const cmd = read('commands/trekplan.md');
+  const orch = read('agents/planning-orchestrator.md');
+  for (const [name, doc] of [['commands/trekplan.md', cmd], ['agents/planning-orchestrator.md', orch]]) {
+    assert.ok(
+      doc.includes('--stdin'),
+      `${name} Phase 9 must pipe reviewer findings into plan-review-dedup.mjs via --stdin (reviewers are read-only)`,
+    );
+    assert.ok(
+      !doc.includes('/tmp/plan-critic-out.json') && !doc.includes('/tmp/scope-guardian-out.json'),
+      `${name} must NOT instruct the read-only reviewers to Write /tmp/*-out.json — they have no Write tool (defect #1)`,
+    );
+  }
+  for (const agentFile of ['agents/plan-critic.md', 'agents/scope-guardian.md']) {
+    const a = read(agentFile);
+    assert.ok(
+      a.includes('"findings"') && a.includes('"rule_key"') && a.includes('"agent"'),
+      `${agentFile} must declare a machine-readable json findings block (agent + findings + rule_key) for the Phase-9 dedup helper`,
+    );
+  }
+});
+
 // --- S20 — anti-false-claim: orchestrator docs must not claim ALL sub-agents run on Sonnet ---
 //
 // All named swarm agents are pinned `model: opus` (operator decision 40d8742;