fix: ffmpeg version prefix, .gz legacy format, iterm2 regex

- ffmpeg: add version_prefix = b to strip 'b' from tags (b6.0 → 6.0)
- legacy.go: add .gz to legacyFormats for bare gzipped binaries
- iterm2: broaden regex to handle preview/beta variants, skip empty
  versions

Match count: 75/106

ffmpeg/releases.conf

@@ -2,3 +2,4 @@ source = github
 owner = eugeneware
 repo = ffmpeg-static
 asset_filter = ffmpeg
+version_prefix = b

internal/classifypkg/classifypkg.go

@@ -814,6 +814,10 @@ func classifyITerm2Dist(d *rawcache.Dir) ([]storage.Asset, error) {
 			continue
 		}
 
+		if entry.Version == "" {
+			continue
+		}
+
 		filename := filepath.Base(entry.URL)
 
 		assets = append(assets, storage.Asset{

internal/releases/iterm2dist/iterm2dist.go

@@ -26,7 +26,7 @@ type Entry struct {
 }
 
 var linkRe = regexp.MustCompile(`href="(https://iterm2\.com/downloads/[^"]*\.zip)"`)
-var versionRe = regexp.MustCompile(`iTerm2[-_]v?(\d+(?:_\d+)*)(?:[-_]?beta(\d+))?\.zip`)
+var versionRe = regexp.MustCompile(`iTerm2[-_]v?(\d+(?:_\d+)*)(?:[-_]?(?:beta|preview)[-_]?(\d*))?\.zip`)
 
 // Fetch retrieves iTerm2 releases by scraping the downloads page.
 //

internal/storage/legacy.go

@@ -86,6 +86,7 @@ var legacyFormats = map[string]bool{
 	".exe.xz":  true,
 	".dmg":     true,
 	".app.zip": true,
+	".gz":      true,
 	"git":      true,
 }