[AZ-299] C7 OnnxTrtEpRuntime: ORT + TRT EP fallback strategy

Land the fallback InferenceRuntime strategy that satisfies C7-IT-05:
when the TRT-direct path (AZ-298) cannot deserialise a cached engine
or when the operator explicitly selects ORT, the system stays in the
air at degraded latency rather than dropping the request. Conforms to
the AZ-297 Protocol; current_runtime_label() == "onnx_trt_ep".

Production
- onnx_trt_ep_runtime.py: compile_engine is a no-op returning an
  EngineCacheEntry pointing at the source .onnx; deserialize_engine
  is gate-first for .engine entries and gate-skip for .onnx, builds
  an ORT InferenceSession with the provider list
  [TensorrtExecutionProvider, CUDAExecutionProvider,
  CPUExecutionProvider], stages cached engines into the ORT TRT EP
  cache directory via symlink-or-copy, warms up with one session.run
  after construction, and honours config.inference.ort_disallow_cpu_
  fallback by raising EngineDeserializeError when the active provider
  resolves to CPU; infer emits a one-shot c7.fallback_to_onnx_trt_ep
  WARN log plus gcs_alert callback on first call when is_fallback=
  True; release_engine is idempotent. _build_provider_args is the
  single point that pins TRT EP option-key names (Risk-3) and caps
  trt_max_workspace_size at gpu_memory_budget_bytes // 4 (AC-8).
- config.py: adds ort_trt_cache_dir (validated non-empty) and
  ort_disallow_cpu_fallback to C7InferenceConfig.
- fdr_client/records.py: adds c7.fallback_to_onnx_trt_ep and
  c7.cpu_fallback FDR record kinds.

Tests
- test_onnx_trt_ep_runtime.py: covers AC-1..AC-8 + Risk-2 CPU-fallback
  alert + Risk-3 option-key pin + NFR-reliability error rewrap; Tier-1
  via fake ORT session; Tier-2 placeholders skip on macOS dev for
  numerical FP16 comparison and session-creation perf NFR.
- test_protocol_conformance.py: drops onnx_trt_ep from the missing-
  module parametrize now that the module ships.
- test_az272_fdr_record_schema.py: extends per-kind fixture builder
  to cover the two new C7 FDR kinds in the roundtrip / schema-version
  AC tests.

Docs
- module-layout.md: replaces the pending onnx_trt_runtime row with
  the shipped onnx_trt_ep_runtime row + capabilities list.
- batch_32_cycle1_report.md + reviews/batch_32_review.md: full batch
  + self-review (PASS_WITH_WARNINGS, 4 Low findings accepted).

Tests run: c7_inference 139 passing + 17 Tier-2 skips; combined unit
suite (excluding pending components) 529 passing, 19 env-skipped.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/unit/c7_inference/test_protocol_conformance.py

@@ -302,7 +302,7 @@ def test_ac5_build_inference_runtime_flag_off_no_import(
     sorted(
         rt
         for rt in _STRATEGY_MODULES
-        if rt not in {"pytorch_fp16", "tensorrt"}
+        if rt not in {"pytorch_fp16", "tensorrt", "onnx_trt_ep"}
     ),
 )
 def test_ac5_build_inference_runtime_flag_on_but_module_missing(
@@ -310,12 +310,12 @@ def test_ac5_build_inference_runtime_flag_on_but_module_missing(
 ) -> None:
     """``BUILD_*=ON`` but the strategy module hasn't been written yet.
 
-    ``pytorch_fp16`` (AZ-300) and ``tensorrt`` (AZ-298) are excluded —
-    both shipped their concrete modules and are covered by
-    ``test_pytorch_fp16_runtime.test_ac1_protocol_conformance`` and
-    ``test_tensorrt_runtime.test_ac1_protocol_conformance``. Only
-    ``onnx_trt_ep`` (AZ-299) remains pending; this test still guards
-    its factory path.
+    AZ-298 (TensorrtRuntime), AZ-299 (OnnxTrtEpRuntime), and AZ-300
+    (PytorchFp16Runtime) have all shipped their concrete modules and
+    are excluded; their protocol conformance is covered in the
+    per-strategy test files. This parameterisation guards the factory
+    path for any future strategy whose `BUILD_*` flag is wired in
+    `inference_factory._RUNTIME_TO_MODULE` ahead of its module landing.
     """
     _, _, flag = _STRATEGY_MODULES[runtime]
     monkeypatch.setenv(flag, "ON")