docs: add project STATE.md

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

.planning/STATE.md

@@ -0,0 +1,41 @@
+# Project State
+
+## Project Reference
+
+See: .planning/PROJECT.md (updated 2026-04-01)
+
+**Core value:** Flight controller must receive valid MAVLink GPS_INPUT at 5-10Hz with position accuracy ≤50m for 80% of frames — without this, the UAV cannot navigate in GPS-denied airspace.
+**Current focus:** Ready to begin Phase 1 (ESKF Core)
+
+## Current Phase
+
+**Phase:** Not started
+**Next action:** Run `/gsd:plan-phase 1` to plan Phase 1 (ESKF Core)
+
+## Roadmap Summary
+
+| Phase | Name | Status |
+|-------|------|--------|
+| 1 | ESKF Core | Pending |
+| 2 | Visual Odometry Pipeline | Pending |
+| 3 | Satellite Matching + GPR | Pending |
+| 4 | MAVLink I/O | Pending |
+| 5 | End-to-End Pipeline Wiring | Pending |
+| 6 | Docker SITL Harness + CI | Pending |
+| 7 | Accuracy Validation | Pending |
+
+## Key Files
+
+- `.planning/PROJECT.md` — project context and requirements
+- `.planning/REQUIREMENTS.md` — 36 v1 requirements with traceability
+- `.planning/ROADMAP.md` — 7-phase execution plan
+- `.planning/codebase/` — codebase map (ARCHITECTURE, CONCERNS, STACK, etc.)
+- `_docs/01_solution/solution.md` — authoritative architecture spec
+- `_docs/00_problem/acceptance_criteria.md` — 43 test scenarios
+
+## Session Notes
+
+- Initialized 2026-04-01
+- Brownfield: scaffold exists (~2800 lines), critical algorithms missing (ESKF, MAVLink, real TRT/cuVSLAM)
+- cuVSLAM + TRT available only on Jetson; dev/CI uses OpenCV ORB stub + MockInferenceEngine
+- Pipeline direction: top-down (API → ESKF → VO → satellite → GPS_INPUT)