fix(ingest): address review round 1 (reclaim queue + tests)

- Register the periodic stalled-job reclaim on a dedicated ingest-maintenance
  queue that every worker drains (any --tier), so reclaim still fires when the
  fast fleet is scaled to zero and only ocr workers run. procrastinate's
  periodic-defer dedup keeps it single-run across drainers.
- escalation: mark `unsupported`/`forced` reason labels as reserved (not raised).
- processor: note that options/progress_callback are intentionally not threaded
  through _parse_pdf_tier yet (symmetric with the inline path).
- tests: assert TieredEscalationStrategy backoff progression (4/8/16/…/300s);
  cover get_ingest_pending per-queue aggregation + the legacy job_counts
  fallback; add an external-path zero-page no-escalation case; use the canonical
  INGEST_QUEUE_FAST instead of the back-compat alias.

Deck #323.

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

tests/unit/test_registry_tiering.py

@@ -388,3 +388,15 @@ def test_evaluate_escalation_terminal_when_no_higher_tier(monkeypatch):
         processor="fast",
     )
     assert r.evaluate_escalation(res, b"%PDF", "fast", _Settings(ocr=True)) is None
+
+
+def test_evaluate_escalation_zero_page_does_not_escalate(monkeypatch):
+    """A zero-page (empty/corrupt) PDF never escalates on the external path."""
+    monkeypatch.setattr(reg_mod, "record_document_classification", MagicMock())
+    r = _registry((_Fake("fast", "fast"), 20), (_Fake("ocr", "ocr"), 5))
+    res = ProcessingResult(
+        text="",
+        metadata={"page_count": 0, "page_boundaries": []},
+        processor="fast",
+    )
+    assert r.evaluate_escalation(res, b"%PDF", "fast", _Settings(ocr=True)) is None