feat(stage2-phase2): structlog hot-path, pytest markers, obs package

Phase 2 deliverables not yet committed from plan execution:
- structlog wired to 10 hot-path files (orchestrator, eskf, components)
- bind_contextvars(correlation_id=frame_id) in process_frame
- obs/logging_config.py: configure_logging(env) JSON/console renderer
- pyproject.toml: structlog>=25.1, --strict-markers, 6 markers registered
- tests/conftest.py: ac(id) validator plugin + pytest_collection hooks

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/gps_denied/components/satellite_matcher/metric_refinement.py

@@ -4,11 +4,11 @@ SAT-03: GSD normalization — downsample camera frame to satellite resolution.
 SAT-04: RANSAC homography → WGS84 position; confidence = inlier_ratio.
 """
 
-import logging
 from typing import List, Optional, Tuple
 
 import cv2
 import numpy as np
+import structlog
 
 from gps_denied.components.satellite_matcher.protocol import IMetricRefinement
 from gps_denied.core.models import IModelManager
@@ -16,7 +16,7 @@ from gps_denied.schemas import GPSPoint
 from gps_denied.schemas.metric import AlignmentResult, ChunkAlignmentResult, Sim3Transform
 from gps_denied.schemas.satellite import TileBounds
 
-logger = logging.getLogger(__name__)
+logger = structlog.get_logger(__name__)
 
 
 class MetricRefinement(IMetricRefinement):