fix: resolve P2 sync noise and cleanup issues

- bd-6pni: Auto-filter tombstoned issues with mismatched prefixes during
  import instead of failing. Tombstones from contributor PRs with different
  test prefixes are pollution and safe to ignore.

- bd-ffr9: Stop recreating deletions.jsonl after tombstone migration.
  Added IsTombstoneMigrationComplete() check to all code paths that write
  to the legacy deletions manifest.

- bd-admx: Fix perpetual "JSONL file hash mismatch" warning. Now clears
  both export_hashes AND jsonl_file_hash when mismatch detected, so the
  warning doesn't repeat.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/delete.go

@@ -685,7 +685,14 @@ func getDeletionsPath() string {
 // recordDeletion appends a deletion record to the deletions manifest.
 // This MUST be called BEFORE deleting from the database to ensure
 // deletion records are never lost.
+// After tombstone migration (bd-ffr9), this is a no-op since inline tombstones
+// are used instead of deletions.jsonl.
 func recordDeletion(id, deleteActor, reason string) error {
+	// bd-ffr9: Skip writing to deletions.jsonl if tombstone migration is complete
+	beadsDir := filepath.Dir(dbPath)
+	if deletions.IsTombstoneMigrationComplete(beadsDir) {
+		return nil
+	}
 	record := deletions.DeletionRecord{
 		ID:        id,
 		Timestamp: time.Now().UTC(),
@@ -698,7 +705,14 @@ func recordDeletion(id, deleteActor, reason string) error {
 // recordDeletions appends multiple deletion records to the deletions manifest.
 // This MUST be called BEFORE deleting from the database to ensure
 // deletion records are never lost.
+// After tombstone migration (bd-ffr9), this is a no-op since inline tombstones
+// are used instead of deletions.jsonl.
 func recordDeletions(ids []string, deleteActor, reason string) error {
+	// bd-ffr9: Skip writing to deletions.jsonl if tombstone migration is complete
+	beadsDir := filepath.Dir(dbPath)
+	if deletions.IsTombstoneMigrationComplete(beadsDir) {
+		return nil
+	}
 	path := getDeletionsPath()
 	for _, id := range ids {
 		record := deletions.DeletionRecord{