feat(web): three-phase progress with live download % on The Floor

Replace the misleading 6-micro-step progress bar with three honest
phases (Searching -> Downloading -> Finishing). Downloading now shows
a live determinate percentage sourced from job.downloadProgress (Slice
A), with a "NN% · done/total tracks" caption when the track count is
known. Searching and Finishing stay indeterminate.

- status.ts: describeJob collapses to {label, kind}; drop step/totalSteps
  and the STAGES array.
- progress-bar.tsx: ProgressBar takes {kind, indeterminate?, percent?,
  caption?} instead of step/total/stageLabel.
- job-row.tsx: JobRow takes a `bar?: ReactNode` slot instead of
  step/total/indeterminate/stageLabel props.
- queue.tsx: builds the per-state bar + meta; downloading meta drops
  the track count (now shown in the bar). Retry button + error note
  from the retry feature preserved exactly.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/_ui/progress-bar.tsx

@@ -1,19 +1,17 @@
 import type { Kind } from "./status";
 
-/** A thin ruled progress bar. `indeterminate` for open-ended stages (searching);
- *  otherwise a discrete step/total fill with a step readout. */
+/** A thin ruled progress bar. `indeterminate` for open-ended phases (searching,
+ *  finishing); otherwise a determinate fill to `percent` with a live readout. */
 export function ProgressBar({
   kind,
-  step,
-  total,
   indeterminate,
-  stageLabel,
+  percent,
+  caption,
 }: {
   kind: Kind;
-  step: number;
-  total: number;
   indeterminate?: boolean;
-  stageLabel?: string;
+  percent?: number;
+  caption?: string;
 }) {
   if (indeterminate) {
     return (
@@ -21,17 +19,17 @@ export function ProgressBar({
         <div className="bar indet">
           <span />
         </div>
-        <div className="pct muted">searching</div>
+        <div className="pct muted">{caption ?? "…"}</div>
       </div>
     );
   }
-  const pct = total > 0 ? Math.round((step / total) * 100) : 0;
+  const pct = Math.min(100, Math.max(0, percent ?? 0));
   return (
     <div className="prog">
       <div className="bar">
         <span style={{ width: `${pct}%` }} />
       </div>
-      <div className="pct">{stageLabel ? `${stageLabel} · step ${step} of ${total}` : `${step}/${total}`}</div>
+      <div className="pct">{caption ?? `${Math.round(percent ?? 0)}%`}</div>
     </div>
   );
 }