fix(#2640): report truthful state_updated + keep progress frontmatter in sync after phase remove (#2974)

* test(#2640): add regression for state_updated false positive + stale progress

Three cases: (1) state_updated reflects actual content change, not just
file existence; (2) progress.total_phases resync'd even when the body lacks
'Total Phases:' (the no-op guard was skipping syncStateFrontmatter);
(3) state_updated is false when STATE.md doesn't exist.

* fix(#2640): report truthful state_updated + force frontmatter resync

Two defects in cmdPhaseRemove:

1. state_updated was fs.existsSync(statePath) — trivially true, since the file
   existed before and readModifyWriteStateMd never deletes it. Now captures
   the boolean return from readModifyWriteStateMd (changed from void to
   boolean: true when content was written, false on no-op).

2. progress.* frontmatter stayed stale when the body lacked 'Total Phases:'
   or 'of N' — readModifyWriteStateMd's no-op guard (#948) skipped
   syncStateFrontmatter when the body transform was unchanged. Now the
   transform forces a body diff when a phase was actually removed, so the
   guard passes and syncStateFrontmatter rebuilds progress.* from the
   post-deletion disk/ROADMAP state.

* fix(#2640): address review — gate forced-diff on targetDir, strengthen assertions

Two MAJOR findings from isolated adversarial review:
1. Forced-diff injected a spurious 'Total Phases:' line even when no directory
   was removed (targetDir === null). Now gated on targetDir !== null.
2. Test #2 asserted 'not 3' instead of '2' — would pass for any wrong count.
   Now asserts exact value. Test #1 strengthened to assert body Total Phases
   and frontmatter total_phases both equal 1.

* chore(#2640): add changeset fragment

* chore(#2640): backfill changeset PR number 2974

---------

Co-authored-by: sim <sim@local>

tests/phase.test.cjs

@@ -2755,6 +2755,81 @@ Plans:
       "surviving row's Plans/Status/Completed cells stay byte-identical; only its leading ordinal renumbers 3->2",
     );
   });
+
+  // ─── #2640: state_updated must reflect actual content change, and progress
+  // frontmatter must be resync'd even when the body lacks 'Total Phases:'. ──
+
+  test('#2640 — state_updated reflects actual content change (not just file existence)', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      `# Roadmap\n\n### Phase 1: A\n**Goal:** x\n\n### Phase 2: B\n**Goal:** y\n`,
+    );
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-a'), { recursive: true });
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '02-b'), { recursive: true });
+    // STATE.md with 'Total Phases:' body field + progress frontmatter
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'STATE.md'),
+      `---\ngsd_state_version: 1.0\ncurrent_phase: 1\nprogress:\n  total_phases: 2\n  completed_phases: 0\n  percent: 0\n---\n\n# State\n\nTotal Phases: 2\n`,
+    );
+
+    const result = runGsdTools('phase remove 2', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+    const out = JSON.parse(result.output);
+    assert.strictEqual(out.state_updated, true, 'state_updated must be true when STATE.md content changed');
+    // Body 'Total Phases:' must be decremented from 2 to 1.
+    const afterState = fs.readFileSync(path.join(tmpDir, '.planning', 'STATE.md'), 'utf-8');
+    const bodyMatch = afterState.match(/^Total Phases:\s*(\d+)/m);
+    assert.ok(bodyMatch, 'body must have Total Phases field after remove');
+    assert.strictEqual(bodyMatch[1], '1', `body 'Total Phases:' must be 1 after removing one of 2 phases; got ${bodyMatch[1]}`);
+    // Frontmatter progress.total_phases must agree.
+    const fmMatch = afterState.match(/total_phases:\s*(\d+)/);
+    assert.ok(fmMatch, 'frontmatter must have total_phases');
+    assert.strictEqual(fmMatch[1], '1', `frontmatter progress.total_phases must be 1; got ${fmMatch[1]}`);
+  });
+
+  test('#2640 — progress.total_phases resync\'d even when body lacks Total Phases', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      `# Roadmap\n\n### Phase 1: A\n**Goal:** x\n\n### Phase 2: B\n**Goal:** y\n\n### Phase 3: C\n**Goal:** z\n`,
+    );
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-a'), { recursive: true });
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '02-b'), { recursive: true });
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '03-c'), { recursive: true });
+    // STATE.md with NO 'Total Phases:' body field, but with progress frontmatter
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'STATE.md'),
+      `---\ngsd_state_version: 1.0\ncurrent_phase: 1\nprogress:\n  total_phases: 3\n  completed_phases: 0\n  percent: 0\n---\n\n# State\n\nNo body phase count here.\n`,
+    );
+
+    const beforeState = fs.readFileSync(path.join(tmpDir, '.planning', 'STATE.md'), 'utf-8');
+    const beforeMatch = beforeState.match(/total_phases:\s*(\d+)/);
+    assert.ok(beforeMatch && beforeMatch[1] === '3', 'precondition: total_phases should be 3');
+
+    const result = runGsdTools('phase remove 2', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+
+    const afterState = fs.readFileSync(path.join(tmpDir, '.planning', 'STATE.md'), 'utf-8');
+    const afterMatch = afterState.match(/total_phases:\s*(\d+)/);
+    assert.ok(afterMatch, `STATE.md frontmatter must still have total_phases after remove; got:\n${afterState}`);
+    // Must be exactly 2 — 3 phases minus 1 removed. Asserting the exact value
+    // catches a wrong count (not just "not 3").
+    assert.strictEqual(afterMatch[1], '2',
+      `total_phases must be exactly 2 after removing one of 3 phases; got ${afterMatch[1]}`);
+  });
+
+  test('#2640 — state_updated is false when STATE.md does not exist', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      `# Roadmap\n\n### Phase 1: A\n**Goal:** x\n`,
+    );
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-a'), { recursive: true });
+    // No STATE.md
+
+    const result = runGsdTools('phase remove 1', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+    const out = JSON.parse(result.output);
+    assert.strictEqual(out.state_updated, false, 'state_updated must be false when no STATE.md exists');
+  });
 });
 
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