fix(stats): fix duplicate-line cleanup edge cases

- Drain the full write queue before scanning, not just one batch, so pending burst rows aren't missed
- Floor lookback-days before the positivity check so a sub-day value no longer collapses to a zero-day window
- Let the parsed cue list override the streaming dedup heuristic wherever it covers a line
- Reject combining --lifetime with --duplicate-lines and non-positive --lookback-days values
- Widen the burst frame bound to catch heavier typesetting while still sparing longer-spaced runs
- Keep the cleanup modal open until the user closes it so they can read the result before it unmounts

docs-site/usage.md

@@ -96,6 +96,7 @@ subminer stats -b                 # Start/reuse the background stats daemon
 subminer stats -s                 # Stop the background stats daemon
 subminer stats cleanup            # Backfill vocabulary metadata, prune stale rows
 subminer stats cleanup -d --dry-run  # Preview cleanup of repeated typeset subtitle lines
+subminer stats cleanup -d --lookback-days 30  # Clean only lines recorded in the last 30 days
 subminer stats rebuild            # Rebuild rollup data
 subminer doctor --refresh-known-words  # Refresh the known-word cache
 subminer logs -e                  # Export a sanitized log ZIP and print its path