feat: progress reporting during corpus embedding

Emit a `… embedded N/total (pct%)` line every 1000 items (and at
completion) so a full --confirm run is observable rather than silent
for its full duration.

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

src/embed.rs

@@ -72,9 +72,16 @@ pub fn build_corpus_embeddings(
         .filter(|t| !store.has(t))
         .cloned()
         .collect();
+    let total = pending.len();
     let mut done = 0;
+    let mut last_report = 0;
     for chunk in pending.chunks(batch.max(1)) {
         done += embed_batch(client, store, model, chunk)?;
+        if done - last_report >= 1000 || done == total {
+            let pct = if total == 0 { 100.0 } else { 100.0 * done as f64 / total as f64 };
+            eprintln!("  … embedded {done}/{total} ({pct:.1}%)");
+            last_report = done;
+        }
     }
     Ok(done)
 }