feat(waveform): generalize high-res compute to every track (Direction B)

Per-track high-res datum keyed by EntryKey in the renamed track-waveforms vault; computed at upload for all tracks, regenerable per-track via CMS, with a re-runnable backfill. Mix read path repointed so it keeps working.

DeepDrftContent/Constants/VaultConstants.cs

@@ -22,8 +22,10 @@ public static class VaultConstants
     public const string Images = "images";
 
     /// <summary>
-    /// Vault name for Mix high-resolution waveform datums, keyed by the mix track's EntryKey.
+    /// Vault name for per-track high-resolution waveform datums, keyed by the track's EntryKey.
+    /// Every track (Mix, Session, Cut) carries one — computed at upload, regenerable on demand.
     /// Distinct from WaveformProfiles (player-bar low-res); same pipeline at higher resolution.
+    /// The datum resolution is duration-derived (≈333 samples/sec, see <c>WaveformResolution</c>).
     /// </summary>
-    public const string MixWaveforms = "mix-waveforms";
+    public const string TrackWaveforms = "track-waveforms";
 }