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/lib/preview/previewSession.svelte.js

@@ -30,6 +30,7 @@ let service = null;
 let unsubscribe = null;
 let focusParts = null; // { coordinator, gateway }
 let demoTicker = null;
+let readPlayerRef = null; // injected with the bridge; app volume source
 
 // ------------------------------------------------------------- gateway ----
 
@@ -50,6 +51,7 @@ export function notePlaybackGeneration() {
 
 /** One-time wiring from state.svelte.js. */
 export function initPreviewBridge({ readPlayer, resumeMain }) {
+    readPlayerRef = readPlayer;
     focusParts = createProductionFocus({
         readPlayer,
         readPlaybackGeneration: () => playbackGeneration,
@@ -81,6 +83,11 @@ export async function openPreview(manifest, { playFull } = {}) {
             focus: focusParts,
         })
     );
+    // Preview volume follows the APP volume (mute = 0) — set it BEFORE the
+    // first load so the opening clip can't blast at the backend default.
+    // The overlay keeps it mirrored live while the modal is open.
+    const p = readPlayerRef?.();
+    if (p) service.setVolume(p.muted ? 0 : (p.volume ?? 0.7));
     previewUi.open = true;
     await service.open({ sessionId: crypto.randomUUID(), manifest });
 }
@@ -176,4 +183,5 @@ export const previewCommands = {
     seek: (ms) => service?.seek(ms),
     setMuted: (v) => service?.setMuted(v),
     playFullTrack: (starter) => service?.playFullTrack(starter),
+    setVolume: (v) => service?.setVolume(v),
 };