fix: previews follow the app volume; volume bar fill always accent

The preview backend never received a volume — clips played at the crate
default (0.7) regardless of the slider, even muted. The session now sets
the preview volume from the app store (mute → 0) before the first load and
mirrors it live while the modal is open; the debug overlay's PREVIEW row
exposes the backend's resting volume as proof.

The player-bar volume (and fallback seek) fill is now always the accent
color — matching the waveform scrubber's played region — stepping up to
the hover shade on hover instead of white-until-hover.

Also syncs package-lock to the soulstream name + alpha version.

src/components/PreviewOverlay.svelte

@@ -18,6 +18,7 @@
         previewCommands,
         closePreview,
     } from "../lib/preview/previewSession.svelte.js";
+    import { player } from "../lib/state.svelte.js";
     import {
         playableManifestIndices,
         playableCursor,
@@ -25,6 +26,14 @@
     } from "../lib/preview/session.js";
     import { accentFromImage } from "../lib/color.js";
 
+    // Preview audio follows the APP volume — mute means silent previews
+    // too. Mirrored live while the modal is open (the session also sets it
+    // once at open, before the first load).
+    $effect(() => {
+        if (!previewUi.open) return;
+        previewCommands.setVolume(player.muted ? 0 : player.volume);
+    });
+
     const st = $derived(previewUi.snapshot);
     const manifest = $derived(st?.manifest ?? null);
     const items = $derived(manifest?.items ?? []);