901b18ee13
Two bugs caused the start/stop loop:
1. The <audio> element was wrapped in {#if audioStore.audioUrl}, so whenever
any reactive state changed (e.g. currentTime ticking), Svelte could destroy
and recreate the element, firing onpause and then the URL effect restarting
playback.
2. Comparing audioEl.src !== url is unreliable — browsers normalise the src
property to a full absolute URL, causing false mismatches every tick.
Fix: make <audio> always present in the DOM (display:none), and track the
loaded URL in a plain local variable (loadedUrl) instead of reading audioEl.src.