fix(newos4): unmeasured skills are untracked, world-model writes verified, skill audit

External review packet (os4-external-review-v4.6.51.html) triaged against the code:
2 findings confirmed and fixed, 4 could not be reproduced and were recorded as such.

- module-memory-graph.js: getStaleSkills() treated a missing lastUsed as 999 days
  unused, so skill-audit recommended archiving every skill (22 of 22). Skills with no
  usage telemetry are now collected by getUntrackedSkills() and never counted stale.
  Live: "Stale: 0" + "Untracked: 22 (no usage telemetry — NOT stale)".
- module-world-model.js: _saveToVFS() ignored fsWriteJSON()'s return value and promoted
  whatever a truthy read returned. Now write -> read-back -> byte compare -> promote,
  with every return checked. Regression test modules/test/test-world-model-save.js
  (red on the old code: promoted=true with errs=[]; green now).
- scripts/newos4-skill-audit.py: 5 mechanical probes (version x3, read_file paging +
  context budget, selection symbols, required scripts, extKeys) + skill presence;
  exits non-zero on drift. 7/7 pass today. Weekly job cb6bc2a16216 runs it Mondays.

Not reproduced (recorded in admin/docs/newos4-external-review-verification-2026-10-23.md):
world_model_query empty-payload throw (live call returns JSON), pipes-as-command-names,
ls skills empty (23 entries via fs.readDir), ~66 agent dirs (4 live).

1 files changed, 91 insertions, 0 deletions

diff --git a/scripts/newos4-skill-audit.py b/scripts/newos4-skill-audit.py
new file mode 100755
index 0000000..c10274c
--- /dev/null
+++ b/scripts/newos4-skill-audit.py
@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+"""Audit newOS4 skill claims against the live tree. Exit 1 on any drift."""
+import json, os, re, subprocess, sys
+
+ROOT = '/var/www/webx11.duckdns.org/spaces/newos4'
+SKILLS = os.path.expanduser('~/.hermes/profiles/webx11/skills/webx11')
+PAIRS = ['newos4-core-module-editing', 'newos4-module-patch-and-verify']
+
+
+def read(p):
+    try:
+        with open(p, encoding='utf-8') as f:
+            return f.read()
+    except Exception:
+        return ''
+
+
+def probe_version():
+    loader = read(os.path.join(ROOT, 'modules/core/module-loader.js'))
+    m = re.search(r"LATEST_VER\s*=\s*'([^']+)'", loader)
+    if not m:
+        return False, 'LATEST_VER not found in module-loader.js'
+    ver = m.group(1)
+    n = read(os.path.join(ROOT, 'main.html')).count(ver)
+    return n == 3, f'{ver} appears {n}x in main.html (expect 3)'
+
+
+def probe_read_file():
+    src = read(os.path.join(ROOT, 'modules/core/module-aiassist.js'))
+    has_offset = 'offset: { type:' in src
+    has_next = 'next_offset' in src
+    m = re.search(r'maxContextTokens\s*=\s*(\d+)', src)
+    return (has_offset and has_next and bool(m)), \
+        f'offset={has_offset} next_offset={has_next} maxContextTokens={m.group(1) if m else None}'
+
+
+def probe_selection():
+    src = read(os.path.join(ROOT, 'modules/ext/filemgr.js'))
+    return ('_multiSelect' in src and '_getSelectedPaths' in src), \
+        f'_multiSelect={"_multiSelect" in src} _getSelectedPaths={"_getSelectedPaths" in src}'
+
+
+def probe_scripts():
+    need = ['scripts/rebuild-bundles.py', 'scripts/lint-no-undef.py',
+            'scripts/newos4-maintain.py', 'scripts/newos4-triage.py']
+    missing = [p for p in need if not os.path.exists(os.path.join(ROOT, p))]
+    return not missing, f'missing={missing or "none"}'
+
+
+def probe_bundle_membership():
+    loader = read(os.path.join(ROOT, 'modules/core/module-loader.js'))
+    return "extKeys = [" in loader, 'extKeys literal present'
+
+
+PROBES = {
+    'version': probe_version,
+    'read_file_contract': probe_read_file,
+    'selection_symbols': probe_selection,
+    'scripts': probe_scripts,
+    'ext_keys': probe_bundle_membership,
+}
+
+
+def main():
+    results, failed = {}, 0
+    for name, fn in PROBES.items():
+        try:
+            ok, detail = fn()
+        except Exception as e:
+            ok, detail = False, f'probe threw: {e}'
+        results[name] = {'ok': ok, 'detail': detail}
+        print(('PASS ' if ok else 'FAIL ') + name + ': ' + detail)
+        failed += 0 if ok else 1
+
+    for pair in PAIRS:
+        p = os.path.join(SKILLS, pair, 'SKILL.md')
+        results['skill_' + pair] = {'ok': os.path.exists(p), 'detail': p}
+        if not os.path.exists(p):
+            print('FAIL skill_' + pair + ': missing ' + p)
+            failed += 1
+
+    out = '/var/lib/webx11/newos4-maintenance/skill-audit.json'
+    os.makedirs(os.path.dirname(out), exist_ok=True)
+    with open(out, 'w', encoding='utf-8') as f:
+        json.dump(results, f, indent=2)
+    print(f'skill audit: {len(PROBES) - failed + len(PAIRS)}/{len(PROBES) + len(PAIRS)} pass')
+    return 1 if failed else 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())