feat(ultraplan-local): add autonomy-gate state machine + manifest schema extensions for skip_commit_check + memory_write

Step 4 of plan-v2 (ultra-pipeline-speedup).

lib/util/autonomy-gate.mjs (NEW)
  5-state machine {idle, gates_on, auto_running, paused_for_gate, completed}
  honoring the --gates flag intent. Re-entry to completed is idempotent.
  Includes CLI shim:
    node lib/util/autonomy-gate.mjs --state X --event Y [--gates true|false]
  → JSON: { ok, next_state | error }, exit 0 on success / 1 on invalid.

lib/parsers/manifest-yaml.mjs (EXTENDED)
  OPTIONAL_KEYS list adds skip_commit_check and memory_write — both boolean,
  default false when absent, MANIFEST_OPTIONAL_TYPE when non-boolean.
  Existing REQUIRED_KEYS contract untouched; existing 9 manifest tests
  still pass.

Tests: 19 (autonomy-gate) + 8 (manifest-schema-extensions) = 27 new.

[skip-docs]

plugins/ultraplan-local/tests/lib/manifest-schema-extensions.test.mjs

@@ -0,0 +1,92 @@
+// tests/lib/manifest-schema-extensions.test.mjs
+// Cover the OPTIONAL_KEYS extension to lib/parsers/manifest-yaml.mjs:
+//   - skip_commit_check  (boolean, default false)
+//   - memory_write       (boolean, default false)
+//
+// Defaults must NOT break the REQUIRED_KEYS contract.
+// Non-boolean values must produce MANIFEST_OPTIONAL_TYPE error.
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { parseManifest, OPTIONAL_KEYS } from '../../lib/parsers/manifest-yaml.mjs';
+
+const BASE = `### Step 1: Cover
+- Manifest:
+  \`\`\`yaml
+  manifest:
+    expected_paths:
+      - lib/foo.mjs
+    min_file_count: 1
+    commit_message_pattern: "^feat:"
+    bash_syntax_check: []
+    forbidden_paths: []
+    must_contain: []`;
+
+function bodyWithExtras(extras) {
+  return `${BASE}\n${extras}\n  \`\`\`\n`;
+}
+
+function bodyOnlyRequired() {
+  return `${BASE}\n  \`\`\`\n`;
+}
+
+test('OPTIONAL_KEYS exports skip_commit_check + memory_write', () => {
+  assert.deepEqual(
+    [...OPTIONAL_KEYS].sort(),
+    ['memory_write', 'skip_commit_check'].sort(),
+    'OPTIONAL_KEYS export drift — pin contract',
+  );
+});
+
+test('absence of optional keys → defaults to false (both fields)', () => {
+  const r = parseManifest(bodyOnlyRequired());
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+  assert.equal(r.parsed.skip_commit_check, false);
+  assert.equal(r.parsed.memory_write, false);
+});
+
+test('skip_commit_check: true honored', () => {
+  const r = parseManifest(bodyWithExtras('    skip_commit_check: true'));
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+  assert.equal(r.parsed.skip_commit_check, true);
+  assert.equal(r.parsed.memory_write, false);
+});
+
+test('memory_write: true honored', () => {
+  const r = parseManifest(bodyWithExtras('    memory_write: true'));
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+  assert.equal(r.parsed.memory_write, true);
+  assert.equal(r.parsed.skip_commit_check, false);
+});
+
+test('both optional fields together — both honored', () => {
+  const r = parseManifest(bodyWithExtras('    skip_commit_check: true\n    memory_write: true'));
+  assert.equal(r.valid, true, JSON.stringify(r.errors));
+  assert.equal(r.parsed.skip_commit_check, true);
+  assert.equal(r.parsed.memory_write, true);
+});
+
+test('skip_commit_check: non-boolean rejected with MANIFEST_OPTIONAL_TYPE', () => {
+  const r = parseManifest(bodyWithExtras('    skip_commit_check: "yes"'));
+  assert.equal(r.valid, false);
+  const found = r.errors.find(e => e.code === 'MANIFEST_OPTIONAL_TYPE');
+  assert.ok(found, `expected MANIFEST_OPTIONAL_TYPE, got: ${JSON.stringify(r.errors)}`);
+  assert.match(found.message, /skip_commit_check/);
+});
+
+test('memory_write: numeric rejected with MANIFEST_OPTIONAL_TYPE', () => {
+  const r = parseManifest(bodyWithExtras('    memory_write: 1'));
+  assert.equal(r.valid, false);
+  const found = r.errors.find(e => e.code === 'MANIFEST_OPTIONAL_TYPE');
+  assert.ok(found, `expected MANIFEST_OPTIONAL_TYPE, got: ${JSON.stringify(r.errors)}`);
+  assert.match(found.message, /memory_write/);
+});
+
+test('extension does NOT break REQUIRED_KEYS contract', () => {
+  const r = parseManifest(bodyOnlyRequired());
+  assert.equal(r.valid, true);
+  for (const k of ['expected_paths', 'min_file_count', 'commit_message_pattern',
+                   'bash_syntax_check', 'forbidden_paths', 'must_contain']) {
+    assert.ok(k in r.parsed, `required key ${k} missing after extension`);
+  }
+});