Fix bd-rb75: Ignore merge artifacts in .beads/.gitignore

.beads/.gitignore

@@ -0,0 +1,24 @@
+# SQLite databases
+*.db
+*.db-journal
+*.db-wal
+*.db-shm
+
+# Daemon runtime files
+daemon.lock
+daemon.log
+daemon.pid
+bd.sock
+
+# Legacy database files
+db.sqlite
+bd.db
+
+# Keep JSONL exports and config (source of truth for git)
+!*.jsonl
+!metadata.json
+!config.json
+
+# Exclude merge artifacts (temporary files from 3-way merge)
+beads.base.jsonl
+beads.left.jsonl