feat: autotag scoring overhaul, dump-based explore index, and lyrics search

Consolidates in-progress work across autotag, explore, and library:

- autotag: beets/Picard-informed scoring engine — ID-first matching, VA
  handling, recommendation tiers, and a merged distance/rank cascade, with
  an eval harness for regression tracking.
- explore: offline MusicBrainz dump import/incremental refresh replaces the
  legacy tier crawl; index-first local search with fuzzy matching and a
  dedicated ranker; disk-free guards for dump downloads.
- library: artist-credit extraction and matching.
- lyrics: owned-library lyric search (FTS) with LRCLIB backfill.

Also: rewrite README to be user-focused, and migrate upstream to
git.ljones.me/yonlu/yellowjacket.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/config/config.go

@@ -174,9 +174,46 @@ func (c *Config) Save() error {
 		return fmt.Errorf("could not marshal config struct: %w", err)
 	}
 
-	err = os.WriteFile(c.filePath, confFileData, 0o644)
+	// Write atomically: marshal into a temp file in the same directory,
+	// then rename it over the target.  os.WriteFile truncates the file
+	// in place before writing, so a crash or kill mid-write (common
+	// during dev restarts) can leave a truncated — often empty — config.
+	// An empty TOML file loads "successfully" as all-defaults and then
+	// gets re-saved as defaults, silently wiping the user's settings.
+	// A temp-file + rename makes the replacement atomic: a reader always
+	// sees either the previous file or the complete new one.
+	tmp, err := os.CreateTemp(path.Dir(c.filePath), "config-*.toml.tmp")
 	if err != nil {
-		return fmt.Errorf("could not write config file (%s): %w", c.filePath, err)
+		return fmt.Errorf("could not create temp config file: %w", err)
+	}
+
+	tmpName := tmp.Name()
+
+	// Best-effort cleanup if we bail before the rename succeeds.
+	defer func() { _ = os.Remove(tmpName) }()
+
+	if _, err := tmp.Write(confFileData); err != nil {
+		_ = tmp.Close()
+
+		return fmt.Errorf("could not write temp config file: %w", err)
+	}
+
+	if err := tmp.Sync(); err != nil {
+		_ = tmp.Close()
+
+		return fmt.Errorf("could not sync temp config file: %w", err)
+	}
+
+	if err := tmp.Close(); err != nil {
+		return fmt.Errorf("could not close temp config file: %w", err)
+	}
+
+	if err := os.Chmod(tmpName, 0o644); err != nil {
+		return fmt.Errorf("could not set config file permissions: %w", err)
+	}
+
+	if err := os.Rename(tmpName, c.filePath); err != nil {
+		return fmt.Errorf("could not replace config file (%s): %w", c.filePath, err)
 	}
 
 	c.logger.Debug("saved config to file", "file", c.filePath)

backend/config/window.go

@@ -1,10 +1,20 @@
 package config
 
 const (
-	// DefaultWidth is the default window width in pixels.
-	DefaultWidth = 512
-	// DefaultHeight is the default window height in pixels.
-	DefaultHeight = 384
+	// DefaultWidth is the default window width in pixels for a fresh
+	// config.  Kept comfortably above the minimum so a first launch
+	// (or a config with no saved size) opens at a usable size rather
+	// than the cramped minimum.
+	DefaultWidth = 1100
+	// DefaultHeight is the default window height in pixels for a fresh config.
+	DefaultHeight = 720
+
+	// MinWidth is the smallest allowed window width in pixels.  Wails
+	// enforces this at runtime; it is also the floor below which a
+	// reported size is treated as bogus and not persisted.
+	MinWidth = 512
+	// MinHeight is the smallest allowed window height in pixels.
+	MinHeight = 384
 )
 
 // WindowConfig holds window size preferences.