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>

nextcloud_mcp_server/document_processors/escalation.py

@@ -53,8 +53,10 @@ class EscalateError(Exception):
     the junk text is never indexed, and it must never be swallowed by a broad
     ``except Exception`` on the indexing path.
 
-    ``reason`` uses the existing escalation label vocabulary:
-    ``empty_text`` | ``low_confidence`` | ``unsupported`` | ``forced``.
+    ``reason`` uses the existing escalation label vocabulary. This PR raises
+    ``empty_text`` (scanned / no text layer) and ``low_confidence`` (junk text
+    layer); ``unsupported`` and ``forced`` are reserved for future callers and
+    not raised yet.
     """
 
     def __init__(self, *, from_tier: str, to_tier: str, reason: str) -> None: