add varying intensity to stream tags

plus improving the tag select dropdown in general

src/lib/types.ts

@@ -1,13 +1,16 @@
 /** A track entry: [timestamp_seconds, artist, title] */
 export type Track = [number, string, string];
 
+// tag -> weight, 1 (light) to 3 (heavy)
+export type TagWeights = Record<string, number>;
+
 /** The summary shape used in sidebar listings. */
 export interface StreamSummary {
     id: string;
     stream_date: number;
     filename: string;
     title: string | null;
-    tags: string[];
+    tags: TagWeights;
     length_seconds: number;
 }