feat(phases 2-7): implement full GPS-denied navigation pipeline

Phase 2 — Visual Odometry:
  - ORBVisualOdometry (dev/CI), CuVSLAMVisualOdometry (Jetson)
  - TRTInferenceEngine (TensorRT FP16, conditional import)
  - create_vo_backend() factory

Phase 3 — Satellite Matching + GPR:
  - SatelliteDataManager: local z/x/y tiles, ESKF ±3σ tile selection
  - GSD normalization (SAT-03), RANSAC inlier-ratio confidence (SAT-04)
  - GlobalPlaceRecognition: Faiss index + numpy fallback

Phase 4 — MAVLink I/O:
  - MAVLinkBridge: GPS_INPUT 15+ fields, IMU callback, 1Hz telemetry
  - 3-consecutive-failure reloc request
  - MockMAVConnection for CI

Phase 5 — Pipeline Wiring:
  - ESKF wired into process_frame: VO update → satellite update
  - CoordinateTransformer + SatelliteDataManager via DI
  - MAVLink state push per frame (PIPE-07)
  - Real pixel_to_gps via ray-ground projection (PIPE-06)
  - GTSAM ISAM2 update when available (PIPE-03)

Phase 6 — Docker + CI:
  - Multi-stage Dockerfile (python:3.11-slim)
  - docker-compose.yml (dev), docker-compose.sitl.yml (ArduPilot SITL)
  - GitHub Actions: ci.yml (lint+pytest+docker smoke), sitl.yml (nightly)
  - tests/test_sitl_integration.py (8 tests, skip without SITL)

Phase 7 — Accuracy Validation:
  - AccuracyBenchmark + SyntheticTrajectory
  - AC-PERF-1: 80% within 50m ✅
  - AC-PERF-2: 60% within 20m ✅
  - AC-PERF-3: p95 latency < 400ms ✅
  - AC-PERF-4: VO drift 1km < 100m ✅ (actual ~11m)
  - scripts/benchmark_accuracy.py CLI

Tests: 195 passed / 8 skipped

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

src/gps_denied/schemas/chunk.py

@@ -5,7 +5,7 @@ from typing import List, Optional
 
 from pydantic import BaseModel
 
-from gps_denied.schemas.flight import GPSPoint
+from gps_denied.schemas import GPSPoint
 
 
 class ChunkStatus(str, Enum):

src/gps_denied/schemas/gpr.py

@@ -5,7 +5,7 @@ from typing import Optional
 import numpy as np
 from pydantic import BaseModel
 
-from gps_denied.schemas.flight import GPSPoint
+from gps_denied.schemas import GPSPoint
 from gps_denied.schemas.satellite import TileBounds
 
 

src/gps_denied/schemas/mavlink.py

@@ -0,0 +1,57 @@
+"""MAVLink I/O schemas (Component — Phase 4)."""
+
+from typing import Optional
+from pydantic import BaseModel
+
+
+class GPSInputMessage(BaseModel):
+    """Full field set for MAVLink GPS_INPUT (#233).
+
+    All numeric fields follow MAVLink units convention:
+      lat/lon in degE7, alt in metres MSL, velocity in m/s.
+    """
+    time_usec: int          # µs since Unix epoch
+    gps_id: int = 0
+    ignore_flags: int = 0   # GPS_INPUT_IGNORE_FLAGS bitmask (0 = use all)
+    time_week_ms: int        # GPS ms-of-week
+    time_week: int           # GPS week number
+    fix_type: int            # 0=no fix, 2=2D, 3=3D
+    lat: int                 # degE7
+    lon: int                 # degE7
+    alt: float               # metres MSL
+    hdop: float
+    vdop: float
+    vn: float                # m/s North
+    ve: float                # m/s East
+    vd: float                # m/s Down
+    speed_accuracy: float    # m/s
+    horiz_accuracy: float    # m
+    vert_accuracy: float     # m
+    satellites_visible: int = 0
+
+
+class IMUMessage(BaseModel):
+    """IMU data decoded from MAVLink ATTITUDE / RAW_IMU."""
+    accel_x: float   # m/s² body-frame X
+    accel_y: float   # m/s² body-frame Y
+    accel_z: float   # m/s² body-frame Z
+    gyro_x: float    # rad/s body-frame X
+    gyro_y: float    # rad/s body-frame Y
+    gyro_z: float    # rad/s body-frame Z
+    timestamp_us: int  # µs
+
+
+class TelemetryMessage(BaseModel):
+    """1-Hz telemetry payload sent as NAMED_VALUE_FLOAT messages."""
+    confidence_score: float   # 0.0–1.0
+    drift_estimate_m: float   # estimated position drift in metres
+    fix_type: int             # current fix_type being sent
+    frames_since_sat: int     # frames since last satellite correction
+
+
+class RelocalizationRequest(BaseModel):
+    """Sent when 3 consecutive frames have no position estimate (MAV-04)."""
+    last_lat: Optional[float] = None    # last known WGS84 lat
+    last_lon: Optional[float] = None    # last known WGS84 lon
+    uncertainty_m: float = 500.0        # position uncertainty radius
+    consecutive_failures: int = 3

src/gps_denied/schemas/metric.py

@@ -5,7 +5,7 @@ from typing import Optional
 import numpy as np
 from pydantic import BaseModel
 
-from gps_denied.schemas.flight import GPSPoint
+from gps_denied.schemas import GPSPoint
 
 
 class AlignmentResult(BaseModel):