fix(newos4): empty-pipeline crash, stacks in reports, frame in digest + dashboard (v4.6.55)

Root cause: splitPipe() splits on every '|', so `help |`, `| wc -l`, `a || b` produced a stage with
no argv and executePipeChain() called parts[0].toLowerCase() on undefined — 989 occurrences, first
filed 2026-10-20, unfixable from the report because bug reports dropped the stack that named
executePipeChain:3955. Same unguarded read existed in _classify().

- terminal.js: _classify() returns an inert classification for empty argv; executePipeChain()
  parses each stage once, filters stages with no argv (so the last real stage stays final), warns
  only when the whole pipeline is empty. Last-stage test now compares against the filtered length.
- module-system.js: `bug` diagnostics include the stack (10 frames, 1200 chars); auto-filed reports
  carry it too — they are the majority of the inbox and were previously message-only.
- report.php: per-stack 2 KB cap; fingerprint pinned to message/source/count so adding `stack`
  cannot break dedupe against reports filed before today.
- ingest.php: first_frame() parsed once on ingest, stored as `frame` on each signature.
- newos4-triage.py: FRAME| line with the first application frame.
- dashboard.php: frame under each Top Errors row.
- modules/test/test-pipe-guard.js: ordering tripwire (guard must precede the parts[0] read).

Verified: test RED exit=1 -> GREEN exit=0; browser matrix on v4.6.55 (help |, | wc -l,
echo hi || echo bye, ls | | wc -l, |) -> 0 new error signatures, "|" warns;
auto-filed report now carries stack (RPT-...f3e31124, archived after the probe);
frame = modules/core/core-bundle.js:3955:42; maintain OK; skill audit 7/7.

1 files changed, 3 insertions, 0 deletions

diff --git a/scripts/newos4-triage.py b/scripts/newos4-triage.py
index 20016f7..f639359 100755
--- a/scripts/newos4-triage.py
+++ b/scripts/newos4-triage.py
@@ -118,6 +118,7 @@ def build(apply_fix=False):
         'top_real': sorted(
             ({'message': safe(e.get('message'), 200), 'type': e.get('type'),
               'count': int(e.get('count') or 1), 'age_hours': age_hours(e.get('last_seen')),
+              'frame': safe(e.get('frame'), 160),
               'session': safe(e.get('session_id'), 40)} for e in buckets['real']),
             key=lambda x: -x['count'])[:10],
         'new_reports': [{'id': r.get('id'), 'title': safe(r.get('title'), 160),
@@ -151,6 +152,8 @@ def build(apply_fix=False):
         print('check:', f)
     for e in digest['top_real'][:5]:
         print(f"  DATA| top: {e['count']}x {e['type']} ({e['age_hours']}h) {safe(e['message'], 110)}")
+        if e.get('frame'):
+            print(f"  FRAME| {e['frame']}")
     for r in digest['new_reports'][:5]:
         print(f"  DATA| report: {r['id']} {safe(r['title'], 110)}")
     return digest