Add a built-in tag editor for both libraries

A new Tags tab browses either library; songs can be edited one at a time
or several at once (e.g. a whole album, where per-song fields are locked
and differing values are kept unless changed). Review's compare panel
links to the editor for either side.

Tags are read with ffprobe and written with ffmpeg (MP3/ID3, FLAC, M4A,
OGG, Opus). An existing tag is always written under the name the file
already uses, so edits replace values instead of duplicating them (e.g.
raw Vorbis ALBUMARTIST/TRACKNUMBER), totals follow the file's style
("3/12" or a separate TRACKTOTAL), stale alias tags (YEAR next to DATE)
are removed, other tags and cover art are kept, and no encoder tag is
added. Every written file is verified: values must read back and the
decoded audio must be bit-identical.

Hardlinks are respected: a file used by one library is replaced
atomically (old file to quarantine); a file shared with the other
library is updated in place so the link survives, after a verified
backup copy goes to quarantine, with an option to edit only one
library's copy instead. Edits are operations (old -> new values shown in
History) that can be undone; an interrupted in-place edit is rolled back
on startup. Dry run applies. Migration 6 stores operation details.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/store/models.go

@@ -623,27 +623,28 @@ func (s *Store) Summary(ctx context.Context, pairID int64) (Summary, error) {
 // ---- operations ----
 
 type Operation struct {
-	ID             int64  `json:"id"`
-	PairID         int64  `json:"pair_id"`
-	Action         string `json:"action"`
-	RelMaster      string `json:"rel_master"`
-	RelSlave       string `json:"rel_slave"`
-	RelNew         string `json:"rel_new"`
-	MatchKind      string `json:"match_kind"`
-	MatchReason    string `json:"match_reason"`
-	LinkPreexisted bool   `json:"link_preexisted"`
-	QuarantinePath string `json:"quarantine_path"`
-	QuarantineSide string `json:"quarantine_side"`
-	TmpPath        string `json:"-"`
-	Bytes          int64  `json:"bytes"`
-	DryRun         bool   `json:"dry_run"`
-	Trigger        string `json:"trigger"`
-	Status         string `json:"status"`
-	Error          string `json:"error"`
-	CreatedAt      int64  `json:"created_at"`
-	FinishedAt     *int64 `json:"finished_at"`
-	UndoneAt       *int64 `json:"undone_at"`
-	PurgedAt       *int64 `json:"purged_at"`
+	ID             int64           `json:"id"`
+	PairID         int64           `json:"pair_id"`
+	Action         string          `json:"action"`
+	RelMaster      string          `json:"rel_master"`
+	RelSlave       string          `json:"rel_slave"`
+	RelNew         string          `json:"rel_new"`
+	MatchKind      string          `json:"match_kind"`
+	MatchReason    string          `json:"match_reason"`
+	LinkPreexisted bool            `json:"link_preexisted"`
+	Detail         json.RawMessage `json:"detail,omitempty"`
+	QuarantinePath string          `json:"quarantine_path"`
+	QuarantineSide string          `json:"quarantine_side"`
+	TmpPath        string          `json:"-"`
+	Bytes          int64           `json:"bytes"`
+	DryRun         bool            `json:"dry_run"`
+	Trigger        string          `json:"trigger"`
+	Status         string          `json:"status"`
+	Error          string          `json:"error"`
+	CreatedAt      int64           `json:"created_at"`
+	FinishedAt     *int64          `json:"finished_at"`
+	UndoneAt       *int64          `json:"undone_at"`
+	PurgedAt       *int64          `json:"purged_at"`
 }
 
 // Operation actions.
@@ -653,6 +654,7 @@ const (
 	ActBuild   = "build"   // master file linked into the slave (fresh library)
 	ActRemove  = "remove"  // slave hardlink removed (master copy kept)
 	ActRename  = "rename"  // slave folder renamed to the master's spelling
+	ActTags    = "tags"    // tags of a file edited
 )
 
 // Operation statuses.
@@ -665,13 +667,17 @@ const (
 )
 
 const opCols = `id, pair_id, action, rel_master, rel_slave, rel_new, quarantine_path, quarantine_side, tmp_path, bytes,
-	dry_run, trigger, status, error, created_at, finished_at, undone_at, purged_at, match_kind, match_reason, link_preexisted`
+	dry_run, trigger, status, error, created_at, finished_at, undone_at, purged_at, match_kind, match_reason, link_preexisted, detail`
 
 func scanOp(r scanner) (Operation, error) {
 	var o Operation
 	var fin, und, pur sql.NullInt64
+	var detail string
 	err := r.Scan(&o.ID, &o.PairID, &o.Action, &o.RelMaster, &o.RelSlave, &o.RelNew, &o.QuarantinePath, &o.QuarantineSide,
-		&o.TmpPath, &o.Bytes, &o.DryRun, &o.Trigger, &o.Status, &o.Error, &o.CreatedAt, &fin, &und, &pur, &o.MatchKind, &o.MatchReason, &o.LinkPreexisted)
+		&o.TmpPath, &o.Bytes, &o.DryRun, &o.Trigger, &o.Status, &o.Error, &o.CreatedAt, &fin, &und, &pur, &o.MatchKind, &o.MatchReason, &o.LinkPreexisted, &detail)
+	if detail != "" {
+		o.Detail = json.RawMessage(detail)
+	}
 	if fin.Valid {
 		o.FinishedAt = &fin.Int64
 	}
@@ -687,10 +693,10 @@ func scanOp(r scanner) (Operation, error) {
 func (s *Store) CreateOp(ctx context.Context, o *Operation) error {
 	o.CreatedAt = now()
 	res, err := s.DB.ExecContext(ctx, `INSERT INTO operations (pair_id, action, rel_master, rel_slave, rel_new, quarantine_path,
-		quarantine_side, tmp_path, bytes, dry_run, trigger, status, error, created_at, match_kind, match_reason, link_preexisted)
-		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+		quarantine_side, tmp_path, bytes, dry_run, trigger, status, error, created_at, match_kind, match_reason, link_preexisted, detail)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
 		o.PairID, o.Action, o.RelMaster, o.RelSlave, o.RelNew, o.QuarantinePath, o.QuarantineSide, o.TmpPath, o.Bytes,
-		o.DryRun, o.Trigger, o.Status, o.Error, o.CreatedAt, o.MatchKind, o.MatchReason, o.LinkPreexisted)
+		o.DryRun, o.Trigger, o.Status, o.Error, o.CreatedAt, o.MatchKind, o.MatchReason, o.LinkPreexisted, string(o.Detail))
 	if err != nil {
 		return err
 	}
@@ -800,3 +806,21 @@ func (s *Store) ExpiredQuarantine(ctx context.Context, pairID, cutoff int64) ([]
 	}
 	return out, rows.Err()
 }
+
+// MatchesByMaster lists the matches of a pair that point at a master file.
+func (s *Store) MatchesByMaster(ctx context.Context, pairID int64, relMaster string) ([]Match, error) {
+	rows, err := s.DB.QueryContext(ctx, `SELECT `+matchCols+` FROM matches WHERE pair_id = ? AND rel_master = ?`, pairID, relMaster)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Match
+	for rows.Next() {
+		m, err := scanMatch(rows)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, m)
+	}
+	return out, rows.Err()
+}