format: restore the hls-ts sniff and assert adapter capabilities

Sniff identifies TS assets for the coming policy-driven alignment even
though nothing reaches it through repack today. Compile-time assertions
now state each adapter's capabilities explicitly.

weed/format/hlsts/hlsts.go

@@ -23,6 +23,8 @@ const (
 	// interior chunk cuts land on packet boundaries.
 	TSPacketSize = 188
 
+	tsSyncByte = 0x47
+
 	PlaylistContentType = "application/vnd.apple.mpegurl"
 	MediaContentType    = "video/MP2T"
 )
@@ -33,8 +35,21 @@ func init() {
 
 type Adapter struct{}
 
+var (
+	_ format.Sniffer        = Adapter{}
+	_ format.SidecarIndexer = Adapter{}
+	_ format.Viewer         = Adapter{}
+)
+
 func (Adapter) Name() string { return FormatName }
 
+func (Adapter) Sniff(h format.Hint) bool {
+	if len(h.Head) > TSPacketSize {
+		return h.Head[0] == tsSyncByte && h.Head[TSPacketSize] == tsSyncByte
+	}
+	return len(h.Head) > 0 && h.Head[0] == tsSyncByte
+}
+
 // playlistInfo is the adapter payload: what the generated playback playlist
 // needs beyond the extent sizes.
 type playlistInfo struct {

weed/format/hlsts/hlsts_test.go

@@ -168,6 +168,18 @@ func TestViewSegmentHonorsMediaSequence(t *testing.T) {
 	}
 }
 
+func TestSniff(t *testing.T) {
+	head := make([]byte, 400)
+	head[0], head[TSPacketSize] = tsSyncByte, tsSyncByte
+	if !(Adapter{}).Sniff(format.Hint{Head: head}) {
+		t.Fatalf("Sniff() rejected TS head")
+	}
+	head[TSPacketSize] = 0
+	if (Adapter{}).Sniff(format.Hint{Head: head}) {
+		t.Fatalf("Sniff() accepted non-TS head")
+	}
+}
+
 // The ingest bound admits mediaSequence = MaxInt64-(count-1); the payload
 // decoder must accept the same boundary or every view of such an asset fails.
 func TestMediaSequenceBoundaryRoundTrip(t *testing.T) {

weed/format/parquet/parquet.go

@@ -25,6 +25,11 @@ func init() {
 
 type Adapter struct{}
 
+var (
+	_ format.Sniffer = Adapter{}
+	_ format.Indexer = Adapter{}
+)
+
 func (Adapter) Name() string { return FormatName }
 
 func (Adapter) Sniff(h format.Hint) bool {