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, 16 insertions, 0 deletions

diff --git a/api/debug/ingest.php b/api/debug/ingest.php
index 7388bce..98354fe 100644
--- a/api/debug/ingest.php
+++ b/api/debug/ingest.php
@@ -80,6 +80,20 @@ function norm_ts($s, $fallback) {
     return gmdate('c', $t);   // always +00:00, never Z
 }
 
+// Where did it happen? Parsed ONCE here so the digest (Python) and the dashboard (PHP) read the
+// same value instead of re-implementing this regex twice. Returns 'modules/core/x.js:12:3'.
+function first_frame($stack) {
+    if (!is_string($stack) || $stack === '') return null;
+    foreach (preg_split('/\R/', $stack) as $i => $line) {
+        if ($i === 0 || !preg_match('/^\s+at /', $line)) continue;   // line 0 is "TypeError: ..."
+        if (preg_match('#([\w./-]+\.js)(?:\?v=[\w.]+)?:(\d+):(\d+)#', $line, $m)) {
+            $p = preg_replace('#^.*?/spaces/newos4/#', '', $m[1]);
+            return $p . ':' . $m[2] . ':' . $m[3];
+        }
+    }
+    return null;
+}
+
 $processed = 0;   // entries handled (NOT occurrences) — the client's truncation warning uses this
 foreach ($errors as $e) {
     $processed++;
@@ -103,6 +117,7 @@ foreach ($errors as $e) {
             $allErrors[$idx]['ingested_at'] = $now;
             if (!empty($e['stack'])) {
                 $allErrors[$idx]['stack'] = substr($e['stack'], 0, 2000);
+                $allErrors[$idx]['frame'] = first_frame($e['stack']) ?? ($allErrors[$idx]['frame'] ?? null);
             }
             $ingested += $delta;
         }
@@ -118,6 +133,7 @@ foreach ($errors as $e) {
         'source' => $e['source'] ?? '',
         'module' => $e['module'] ?? null,
         'stack' => isset($e['stack']) ? substr($e['stack'], 0, 2000) : null,
+        'frame' => first_frame($e['stack'] ?? null),
         'session_id' => $sessionId,
         'count' => $delta,
         'first_seen' => norm_ts($e['firstSeen'] ?? null, $now),