[AZ-300] Implement PytorchFp16Runtime — C7 simple-baseline strategy

AZ-300 mandatory simple-baseline InferenceRuntime (eager FP16 PyTorch).
Implements the AZ-297 Protocol; current_runtime_label returns
"pytorch_fp16". Numerical reference every fancier C7 strategy (AZ-298
TRT, AZ-299 ORT) is measured against, and the only viable runtime for
Tier-1 workstation Docker where TRT is non-trivial to install.

Production code (new):
 - components/c7_inference/pytorch_fp16_runtime.py — runtime +
   PytorchEngineHandle + output-shape adapter
 - components/c7_inference/architecture_registry.py — torch-free
   register_architecture / default_registry / ArchitectureFactory
   (Risk-1 mitigation: no L2->L3 back-edge from C7 into per-backbone
   code)
 - components/c7_inference/__init__.py — re-exports the registry
   mechanism. Still does NOT import the concrete strategy module
   (Invariant I-5)
 - components/c7_inference/config.py — adds per_frame_debug_log bool
   field (gates the DEBUG per-frame latency log)

Tests (new): tests/unit/c7_inference/test_pytorch_fp16_runtime.py
covers AC-1..AC-8 + NFRs. AC-1/2/6/7 + thermal/release/registry
guards run unconditionally (17 tests); AC-3/4/5/8 +
NFR-perf-deserialize + NFR-reliability-eval-mode require CUDA and
skip on Tier-1 CI / macOS dev.

Tests (modified):
 - test_protocol_conformance.py — narrowed
   test_ac5_build_inference_runtime_flag_on_but_module_missing
   parametrisation to exclude pytorch_fp16 (now-built); TRT / ORT
   still covered until AZ-298 / AZ-299 ship.

CI: .github/workflows/ci.yml lint + unit jobs now install
'-e .[dev,inference]' because mypy + pytest need torch + torchvision +
onnxruntime on the runner.

Three task-spec -> as-built deltas documented in
_docs/02_tasks/done/AZ-300_c7_pytorch_baseline.md Implementation Notes:
 1. Constructor conforms to AZ-297 factory shape (config positional;
    thermal_publisher + registry + clock keyword-only optionals).
    AZ-302 will update the factory to thread thermal_publisher.
 2. Architecture registry uses extras["model_name"] as lookup key
    (avoids touching the frozen BuildConfig / EngineCacheEntry DTOs).
 3. Warm-up forward deferred to AZ-300 tier-2 follow-up — the zero-arg
    registry has no per-backbone input-shape metadata.

Suite: 1120 passed / 10 skipped (CUDA + Tier-2 + cmake / actionlint
environment gates). No regressions in non-c7_inference areas.

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

tests/unit/c7_inference/test_protocol_conformance.py

@@ -33,10 +33,12 @@ from gps_denied_onboard.components.c7_inference import (
     OptimizationProfile,
     OutOfMemoryError,
     PrecisionMode,
-    RuntimeError as C7RuntimeError,
     TelemetryUnavailableError,
     ThermalState,
 )
+from gps_denied_onboard.components.c7_inference import (
+    RuntimeError as C7RuntimeError,
+)
 from gps_denied_onboard.components.c7_inference.config import KNOWN_RUNTIMES
 from gps_denied_onboard.config.schema import Config, ConfigError
 from gps_denied_onboard.runtime_root.errors import RuntimeNotAvailableError
@@ -44,7 +46,6 @@ from gps_denied_onboard.runtime_root.inference_factory import (
     build_inference_runtime,
 )
 
-
 _CONTRACT_PATH = (
     Path(__file__).resolve().parents[3]
     / "_docs/02_document/contracts/c7_inference/inference_runtime_protocol.md"
@@ -296,10 +297,21 @@ def test_ac5_build_inference_runtime_flag_off_no_import(
     assert module_name not in sys.modules
 
 
-@pytest.mark.parametrize("runtime", sorted(_STRATEGY_MODULES))
+@pytest.mark.parametrize(
+    "runtime",
+    sorted(rt for rt in _STRATEGY_MODULES if rt != "pytorch_fp16"),
+)
 def test_ac5_build_inference_runtime_flag_on_but_module_missing(
     monkeypatch, strategy_module_cleanup, runtime
 ) -> None:
+    """``BUILD_*=ON`` but the strategy module hasn't been written yet.
+
+    ``pytorch_fp16`` is excluded because AZ-300 shipped its concrete
+    module — the corresponding case is covered by
+    ``test_pytorch_fp16_runtime.test_ac1_protocol_conformance`` which
+    constructs the real strategy. The TRT / ORT runtimes (AZ-298 /
+    AZ-299) remain pending; this test still guards their factory path.
+    """
     _, _, flag = _STRATEGY_MODULES[runtime]
     monkeypatch.setenv(flag, "ON")
     config = _config_with_runtime(runtime)