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, 5 insertions, 0 deletions

diff --git a/modules/ext/skill-pack-core.js b/modules/ext/skill-pack-core.js
index f204e70..5c317a4 100644
--- a/modules/ext/skill-pack-core.js
+++ b/modules/ext/skill-pack-core.js
@@ -1054,8 +1054,10 @@ class SkillPackCoreModule {
         // 1. Stale check
         const mg = this.terminal?.moduleManager?.modules?.['MemoryGraphModule'];
         var staleSkills = [];
+        var untracked = [];
         if (mg && typeof mg.getStaleSkills === 'function') {
             staleSkills = mg.getStaleSkills();
+            untracked = (typeof mg.getUntrackedSkills === 'function') ? mg.getUntrackedSkills() : [];
         }
         for (var s of staleSkills) {
             if (!index[s.name] || index[s.name].immune) continue;
@@ -1093,6 +1095,9 @@ class SkillPackCoreModule {
         this.terminal.print('Total skills:   ' + allNames.length, 'info');
         this.terminal.print('Healthy:        ' + healthy, 'success');
         this.terminal.print('Stale:          ' + stale.length + (stale.length > 0 ? '  (' + stale.join(', ') + ')' : ''), stale.length > 0 ? 'warning' : 'info');
+        if (untracked.length) {
+            this.terminal.print('Untracked:      ' + untracked.length + '  (no usage telemetry — NOT stale)', 'info');
+        }
         this.terminal.print('Duplicates:     ' + duplicates.length + (duplicates.length > 0 ? '  (' + duplicates.join(', ') + ')' : ''), duplicates.length > 0 ? 'warning' : 'info');
         this.terminal.print('Broken refs:    ' + brokenRefs, brokenRefs > 0 ? 'error' : 'info');
         this.terminal.print('', '');