fix(seedgo): readme check-ignore must match dir-only patterns on clean checkout (DPLAN-0195)

The last 1%: 7 branches scored 99% in CI while 100% locally. Root cause proven
by reproducing CI's exact path (tracked-only tree + real .git): .gitignore
dir-only patterns (trailing slash — logs/, **/*_json/, .trinity/) do NOT match
via 'git check-ignore <bare-path>' when the path is absent from disk (clean
checkout), because git cannot infer 'directory' to apply a dir-only pattern.
The working tree has those dirs on disk, so it matched there — the exact
working-tree-vs-clean-checkout divergence.

_is_gitignored now also tests the trailing-slash form; all 7 readme failures
(cli_json/logs/artifacts/.trinity/ etc flagged 'missing on disk') clear.
Regression test builds a real git repo with dir-only patterns + non-existent
paths. CI gate also now prints failing standards + check messages (says WHY).

Verified: clean tree w/ real .git 13/13 100%; working tree 13/13 100%; seedgo
1053 tests green; pyright 0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/scripts/seedgo_audit.py

@@ -30,12 +30,27 @@ for branch in branches:
     avg = result.get("average", 0)
     print(f"  {branch['name']:>12}: {avg:.0f}%")
     if avg < THRESHOLD:
-        failed.append((branch["name"], avg))
+        failed.append((branch["name"], avg, result))
 
 if failed:
     print(f"\nFAILED: {len(failed)} branch(es) below {THRESHOLD}%")
-    for name, score in failed:
+    for name, score, result in failed:
         print(f"  {name}: {score:.0f}%")
+        # Name the failing standards + the specific checks that did not pass,
+        # so CI logs say WHY (not just the percentage). Critical for diagnosing
+        # working-tree-vs-clean-checkout divergence.
+        scores = result.get("scores", {})
+        results = result.get("results", {})
+        for std, sc in scores.items():
+            if sc < 100:
+                checks = results.get(std, {}).get("checks", [])
+                msgs = [
+                    c.get("message", "")
+                    for c in checks
+                    if not c.get("passed", True)
+                ]
+                detail = " | ".join(m for m in msgs if m)[:400]
+                print(f"      └ {std}: {sc:.0f}%  {detail}")
     sys.exit(1)
 else:
     print(f"\nAll {len(branches)} branches pass (>={THRESHOLD}%)")