refactor(ingest): doc legacy ocr queue; fix docstrings + getattr guard

Address claude-review round 2 on #922:

- Legacy `ingest-ocr` tier resolution (important 1): document why it deliberately
  resolves to `fast` rather than mapping to `ocr-upstream` — stranded pre-split
  jobs re-extract empty and re-escalate via the ladder to the cheap
  `ocr-incluster` rung, keeping them OFF the paid upstream rung. Added a
  tier_for_queue(LEGACY_INGEST_QUEUE_OCR) == "fast" assertion.
- Double get_settings() in `_get_batch_client` (important 2): bind once to a local.
- Stale docstrings (important 3): OcrProcessor (serves both rungs now),
  _tier_available (both OCR rungs gated), evaluate_escalation (targets
  ocr-incluster, falls through to ocr-upstream).
- Misconfigured model_setting (nit 5): OcrProcessor.__init__ raises ValueError on
  an unknown settings attr (fail-fast at startup vs AttributeError mid-OCR); also
  removes the dynamic-getattr static-analysis smell SonarCloud flagged.
- Redundant guard (nit 4): kept `and ocr_tier is not None` — it's required for ty
  to narrow ocr_tier to str for record_document_escalation; added a comment.
- Test gap (nit 6): added a test pinning the CURRENT incluster-failure ->
  tier-1 fallback (does NOT cascade to upstream) so the future 503-escalation
  change is an explicit diff.

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

nextcloud_mcp_server/document_processors/ocr.py

@@ -287,7 +287,9 @@ def build_ocr_backend(
 
 
 class OcrProcessor(DocumentProcessor):
-    """Tier-3 OCR processor (gateway or direct Mistral backend)."""
+    """OCR processor for both OCR rungs — tier2 in-cluster (gateway-only GPU) and
+    tier3 upstream (gateway or direct Mistral backend). One class, two registered
+    instances bound to different ``(tier, model_setting, gateway_only)``."""
 
     def __init__(
         self,
@@ -303,6 +305,11 @@ class OcrProcessor(DocumentProcessor):
         # gateway-only (its model, e.g. surya, is reachable solely via the
         # gateway); the upstream rung keeps the configurable gateway/mistral
         # selection. surya is NEVER hard-coded here — only a config default.
+        # Fail fast on a misconfigured model_setting (a typo in a constructor call)
+        # so it surfaces at startup, not as an AttributeError mid-OCR. The string
+        # only ever comes from hardcoded defaults in __init__.py, never user input.
+        if not hasattr(Settings, model_setting):
+            raise ValueError(f"Unknown model_setting: {model_setting!r}")
         self._name = name
         self._tier = tier
         self._model_setting = model_setting
@@ -450,9 +457,10 @@ class OcrProcessor(DocumentProcessor):
                 self._batch_client_lock = anyio.Lock()
             async with self._batch_client_lock:
                 if not self._batch_client_resolved:  # double-checked
+                    settings = get_settings()
                     self._batch_client = build_gateway_batch_client(
-                        get_settings(),
-                        model=getattr(get_settings(), self._model_setting),
+                        settings,
+                        model=getattr(settings, self._model_setting),
                     )
                     self._batch_client_resolved = True
         return self._batch_client