gandora: STORAGE.md, the contract between the page and whatever stores its tracks

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K6897PWcUEwHiqZMcVnNF6

ventures/gandora/STORAGE.md

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+# gandora storage contract
+
+The page keeps everything through one object, `db`, in `index.html`. Today it is IndexedDB in the browser; a backend
+replaces it by implementing the same four calls and pointing `db` at the new implementation. Nothing else in the page
+touches storage (`brain.js` reads through `db.all()` too).
+
+```
+db.put(row, store = "tracks")      // create or replace, keyed by row.id
+db.all(store = "tracks")           // every row, newest first (tracks by `made`, stations by `last`)
+db.del(id, store = "tracks")
+db.open()                          // internal; a backend adapter can drop it
+```
+
+Two stores.
+
+## tracks
+
+```
+{
+  id:        "1760998800000-211979153",   // spec.made + "-" + hash32(title); stable, made by the page
+  made:      1760998800000,               // ms epoch, when the DJ wrote it
+  kept:      false,                       // pinned by KEEP (the only pin)
+  plays:     3,                           // play starts + loop passes
+  blob:      Blob,                        // the audio (FLAC from Venice, mp3 from Runware); a backend may return { url } instead
+  spec: {                                 // the song on paper: enough to re-render it anywhere
+    title, tags, lyrics, bpm, key, energy, line,   // what the DJ wrote (tags = the music prompt, <= 500 chars)
+    seed, station, stationId,                      // where it came from
+    reaction: "🔥 ❤️ \"less snare\" [skipped]",     // the listener's reactions, in order; words quoted, skips bracketed
+    guess: 0.71,                                   // the taste net's prediction when it was cooked (optional)
+    plays, id, made                                // mirrored for convenience
+  }
+}
+```
+
+## stations
+
+```
+{
+  id:      "s-1760998800000-211979153",   // "s-" + ms + hash32(seed)
+  seed:    "rainy trains",
+  name:    "Platform Nine",               // chosen by the DJ on the first track, then stable
+  taste:   { like: [...], avoid: [...], notes: [...] },   // last 8 of each, in words, fed to the DJ
+  history: [ { id, title, tags, bpm, key, energy, reaction, made } ],   // last 8 tracks, no blobs
+  made:    1760998800000,
+  last:    1761002400000,                 // touched on every play and reaction
+  played:  23
+}
+```
+
+## what a backend adds
+
+- identity: rows are per listener; `/user/station/track` links need the listener in the key
+- `blob` as a URL the `<audio>` element and the Web Audio analyser can load (same-origin or CORS-enabled)
+- sync: the page calls `db.all()` freely (library, taste, play counts), so cache on the client and keep `all()` cheap
+
+## what stays on the page
+
+The taste net (`brain.js`) trains in the browser from `db.all()` rows; it needs only `spec` + `kept` + `plays`.
+Share links (`?t=`) carry a spec, not an id, so they work with no backend at all; with one, a link can carry the id
+and the backend's audio instead of re-rendering.