fix(pr-daemon): log held hints

A hint withheld because the session is busy left no trace, which reads
identical to no event at all.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

bin/reviewer-poll.ts

@@ -472,6 +472,7 @@ async function evaluate(prs: Pr[], mentioned: Set<string>, budget: { sessions: n
     // holding it costs one cycle and nothing else.
     if (st !== "idle") {
       dirty.add(full.key);
+      log(`holding ${full.key} (${why.join(",") || "no reason"}): ${session.title} is ${st}`);
       continue;
     }