[AZ-266] [AZ-269] [AZ-277] [AZ-280] Cross-cutting log/config + SE3/SHA256 helpers

AZ-266: schema-compliant JSON logging entrypoint, level normalisation,
handler-topology guard, format-error fallback (log_record_schema v1.0.0).
AZ-269: env > YAML > defaults config loader, frozen Config dataclass,
missing-var fail-fast with pointer to .env.example, component-block registry.
AZ-277: GTSAM-backed SE3Utils (matrix<->SE3 + exp/log/adjoint) with strict
orthogonality, dtype, and bottom-row contract enforcement.
AZ-280: atomicwrites-backed write_atomic + independent verify +
order-deterministic aggregate_hash; sidecar format strictness.
pyproject.toml pins gtsam>=4.2,<5.0 and atomicwrites>=1.4,<2.0
(named-backend deps per the AZ-277 / AZ-280 contracts).
139 unit tests pass (44 new). Review verdict: PASS_WITH_WARNINGS;
findings are perf-NFR + journald deferrals, no blocking issues.

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

src/gps_denied_onboard/config/__init__.py

@@ -1,9 +1,24 @@
-"""Config loader + dataclass schemas (owned by AZ-269 / E-CC-CONF).
+"""Config loader + dataclass schemas (E-CC-CONF / AZ-269)."""
 
-Bootstrap creates importable stubs so every component constructor can take a
-config argument from day one.
-"""
+from gps_denied_onboard.config.loader import ENV_KEY_MAP, load_config
+from gps_denied_onboard.config.schema import (
+    Config,
+    ConfigError,
+    FdrConfig,
+    LogConfig,
+    RequiredFieldMissingError,
+    RuntimeConfig,
+    register_component_block,
+)
 
-from gps_denied_onboard.config.schema import RuntimeConfig
-
-__all__ = ["RuntimeConfig"]
+__all__ = [
+    "ENV_KEY_MAP",
+    "Config",
+    "ConfigError",
+    "FdrConfig",
+    "LogConfig",
+    "RequiredFieldMissingError",
+    "RuntimeConfig",
+    "load_config",
+    "register_component_block",
+]