[DART-uXkzecM0umnf] cleanup: remove 53 tracked Golden{Mismatch,RoundTrip}_ debris files

These are GUID-suffixed runtime dump artifacts from GoldenAsync_RoundTrip_*
and GoldenAsync_Mismatch_* tests (GoldenTests.cs lines 34, 65 — generated
via System.Guid.NewGuid()). Never referenced as fixtures. Adds
src/PsBash.Differential.Tests/Goldens/.gitignore so future flaky runs do
not re-commit them.

Verified: GoldenAsync_RoundTrip_WriteThenRead_Matches +
GoldenAsync_Mismatch_ThrowsXunitException both green after cleanup.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: andylbrummer

.dartai-locks.json

@@ -1,17 +1,3 @@
 {
-  "claims": {
-    "uXkzecM0umnf": {
-      "runner_instance_id": "DESKTOP-NPIOPS6-7606",
-      "runner_email": "andybrummer@standardbeagle.com",
-      "claimed_at": "2026-05-15T12:30:00Z",
-      "agent_id": "DESKTOP-NPIOPS6-7606",
-      "parent_loop_id": "PA7u9PKOwWCY",
-      "purpose": "Phase F9: cleanup tracked GoldenMismatch_/GoldenRoundTrip_ debris + gitignore",
-      "source_event": {
-        "loop_id": "PA7u9PKOwWCY",
-        "task_id": "uXkzecM0umnf",
-        "conversation_id": null
-      }
-    }
-  }
+  "claims": {}
 }

src/PsBash.Differential.Tests/Goldens/.gitignore

@@ -0,0 +1,6 @@
+# Runtime-generated golden test artifacts (GUID-suffixed names from
+# GoldenTests.cs). These are dump output from `GoldenAsync_RoundTrip_*` and
+# `GoldenAsync_Mismatch_*` tests, not fixture data. Each run produces new
+# GUIDs; leaving them tracked accretes debris (53 files removed 2026-05-15).
+GoldenMismatch_*.golden.txt
+GoldenRoundTrip_*.golden.txt