fix: plan mode traces the plan, not the git diff

Codex adversarial review caught that plan-eng-review was inheriting
"git diff origin/<base>...HEAD" from the shared resolver, but plan mode
reviews a plan document, not a code diff. Plan mode now says:
"Trace every codepath in the plan" and "Read the plan document."

Ship and review modes keep the git diff instruction.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.agents/skills/gstack-plan-eng-review/SKILL.md

@@ -338,11 +338,11 @@ ls -d test/ tests/ spec/ __tests__/ cypress/ e2e/ 2>/dev/null
 
 3. **If no framework detected:** still produce the coverage diagram, but skip test generation.
 
-**Step 1. Trace every codepath changed** using `git diff origin/<base>...HEAD`:
+**Step 1. Trace every codepath in the plan:**
 
-Read every changed file. For each one, trace how data flows through the code — don't just list functions, actually follow the execution:
+Read the plan document. For each new feature, service, endpoint, or component described, trace how data will flow through the code — don't just list planned functions, actually follow the planned execution:
 
-1. **Read the diff.** For each changed file, read the full file (not just the diff hunk) to understand context.
+1. **Read the plan.** For each planned component, understand what it does and how it connects to existing code.
 2. **Trace data flow.** Starting from each entry point (route handler, exported function, event listener, component render), follow the data through every branch:
    - Where does input come from? (request params, props, database, API call)
    - What transforms it? (validation, mapping, computation)

plan-eng-review/SKILL.md

@@ -346,11 +346,11 @@ ls -d test/ tests/ spec/ __tests__/ cypress/ e2e/ 2>/dev/null
 
 3. **If no framework detected:** still produce the coverage diagram, but skip test generation.
 
-**Step 1. Trace every codepath changed** using `git diff origin/<base>...HEAD`:
+**Step 1. Trace every codepath in the plan:**
 
-Read every changed file. For each one, trace how data flows through the code — don't just list functions, actually follow the execution:
+Read the plan document. For each new feature, service, endpoint, or component described, trace how data will flow through the code — don't just list planned functions, actually follow the planned execution:
 
-1. **Read the diff.** For each changed file, read the full file (not just the diff hunk) to understand context.
+1. **Read the plan.** For each planned component, understand what it does and how it connects to existing code.
 2. **Trace data flow.** Starting from each entry point (route handler, exported function, event listener, component render), follow the data through every branch:
    - Where does input come from? (request params, props, database, API call)
    - What transforms it? (validation, mapping, computation)

scripts/gen-skill-docs.ts

@@ -1313,13 +1313,23 @@ find . -name '*.test.*' -o -name '*.spec.*' -o -name '*_test.*' -o -name '*_spec
 Store this number for the PR body.`);
   }
 
-  // ── Codepath tracing methodology (shared) ──
+  // ── Codepath tracing methodology (shared, with mode-specific source) ──
+  const traceSource = mode === 'plan'
+    ? `**Step 1. Trace every codepath in the plan:**
+
+Read the plan document. For each new feature, service, endpoint, or component described, trace how data will flow through the code — don't just list planned functions, actually follow the planned execution:`
+    : `**${mode === 'ship' ? '1' : 'Step 1'}. Trace every codepath changed** using \`git diff origin/<base>...HEAD\`:
+
+Read every changed file. For each one, trace how data flows through the code — don't just list functions, actually follow the execution:`;
+
+  const traceStep1 = mode === 'plan'
+    ? `1. **Read the plan.** For each planned component, understand what it does and how it connects to existing code.`
+    : `1. **Read the diff.** For each changed file, read the full file (not just the diff hunk) to understand context.`;
+
   sections.push(`
-**${mode === 'ship' ? '1' : 'Step 1'}. Trace every codepath changed** using \`git diff origin/<base>...HEAD\`:
+${traceSource}
 
-Read every changed file. For each one, trace how data flows through the code — don't just list functions, actually follow the execution:
-
-1. **Read the diff.** For each changed file, read the full file (not just the diff hunk) to understand context.
+${traceStep1}
 2. **Trace data flow.** Starting from each entry point (route handler, exported function, event listener, component render), follow the data through every branch:
    - Where does input come from? (request params, props, database, API call)
    - What transforms it? (validation, mapping, computation)

test/gen-skill-docs.test.ts

@@ -425,7 +425,6 @@ describe('TEST_COVERAGE_AUDIT placeholders', () => {
 
   test('all three modes share codepath tracing methodology', () => {
     const sharedPhrases = [
-      'Trace every codepath changed',
       'Trace data flow',
       'Diagram the execution',
       'Quality scoring rubric',
@@ -438,6 +437,12 @@ describe('TEST_COVERAGE_AUDIT placeholders', () => {
       expect(shipSkill).toContain(phrase);
       expect(reviewSkill).toContain(phrase);
     }
+    // Plan mode traces the plan, not a git diff
+    expect(planSkill).toContain('Trace every codepath in the plan');
+    expect(planSkill).not.toContain('git diff origin');
+    // Ship and review modes trace the diff
+    expect(shipSkill).toContain('Trace every codepath changed');
+    expect(reviewSkill).toContain('Trace every codepath changed');
   });
 
   test('all three modes include E2E decision matrix', () => {