ADR-081: Layer 3 mesh plane + Rust mirror trait — all 5 layers landed

Fully implements the remaining deferred pieces of the adaptive CSI mesh
firmware kernel. All 5 layers (Radio Abstraction, Adaptive Controller,
Mesh Sensing Plane, On-device Feature Extraction, Rust handoff) are
now implemented and host-tested end-to-end.

Layer 3 — Mesh Sensing Plane (firmware/esp32-csi-node/main/rv_mesh.{h,c}):
  * 4 node roles: Unassigned / Anchor / Observer / FusionRelay / Coordinator
  * 7 message types: TIME_SYNC, ROLE_ASSIGN, CHANNEL_PLAN,
    CALIBRATION_START, FEATURE_DELTA, HEALTH, ANOMALY_ALERT
  * 3 auth classes: None / HMAC-SHA256-session / Ed25519-batch
  * Payload types: rv_node_status_t (28 B), rv_anomaly_alert_t (28 B),
    rv_time_sync_t (16 B), rv_role_assign_t (16 B),
    rv_channel_plan_t (24 B), rv_calibration_start_t (20 B)
  * 16-byte envelope + payload + IEEE CRC32 trailer
  * Pure rv_mesh_encode()/rv_mesh_decode() plus typed convenience encoders
  * rv_mesh_send_health() + rv_mesh_send_anomaly() helpers

Controller wiring (adaptive_controller.c):
  * Slow loop (30 s default) now emits HEALTH
  * apply_decision() emits ANOMALY_ALERT on transitions to ALERT /
    DEGRADED
  * Role + mesh epoch tracked in module state; epoch bumps on role
    change

Layer 5 — Rust mirror (crates/wifi-densepose-hardware/src/radio_ops.rs):
  * RadioOps trait mirrors rv_radio_ops_t vtable
  * MockRadio backend for offline tests
  * MeshHeader / NodeStatus / AnomalyAlert types mirror rv_mesh.h
  * Byte-identical IEEE CRC32 (poly 0xEDB88320) verified against
    firmware test vectors (0xCBF43926 for "123456789")
  * decode_mesh / decode_node_status / decode_anomaly_alert / encode_health
  * 8 unit tests, including mesh_constants_match_firmware which asserts
    MESH_MAGIC/VERSION/HEADER_SIZE/MAX_PAYLOAD match rv_mesh.h
    byte-for-byte
  * Exported from lib.rs
  * signal/ruvector/train/mat crates untouched — satisfies ADR-081
    portability acceptance test

Tests (all passing):
  test_adaptive_controller:   18/18   (C, decide() 3.2 ns/call)
  test_rv_feature_state:      15/15   (C, CRC32 87 MB/s)
  test_rv_mesh:               27/27   (C, roundtrip 1.0 µs)
  radio_ops::tests (Rust):     8/8
  --- total:                 68/68 assertions green ---

Docs:
  * ADR-081 status flipped to Accepted
  * Implementation-status matrix updated; L3 + Rust mirror both
    marked Implemented
  * Benchmarks table extended with rv_mesh encode+decode roundtrip
  * Verification section updated with cargo test invocation
  * CHANGELOG: two new entries for L3 mesh plane + Rust mirror

Remaining follow-ups (Phase 3.5 polish, not blocking):
  * Mesh RX path (UDP listener + dispatch) on the firmware
  * Ed25519 signing for CHANNEL_PLAN / CALIBRATION_START
  * Hardware validation on COM7

firmware/esp32-csi-node/tests/host/Makefile

@@ -29,7 +29,7 @@ FEATURE_STATE_SRCS := $(MAIN_DIR)/rv_feature_state.c
 # before including the .c. The decide() body itself has no ESP-IDF deps.
 # Simpler: just recompile decide() here via a small shim.
 
-TESTS := test_adaptive_controller test_rv_feature_state
+TESTS := test_adaptive_controller test_rv_feature_state test_rv_mesh
 
 all: $(TESTS)
 
@@ -39,10 +39,19 @@ test_adaptive_controller: test_adaptive_controller.c $(MAIN_DIR)/adaptive_contro
 test_rv_feature_state: test_rv_feature_state.c $(FEATURE_STATE_SRCS) $(MAIN_DIR)/rv_feature_state.h $(MAIN_DIR)/rv_radio_ops.h
 	$(CC) $(CFLAGS) test_rv_feature_state.c $(FEATURE_STATE_SRCS) -o $@ $(LDLIBS)
 
+# Mesh plane encoder/decoder: compile rv_mesh.c with RV_MESH_HOST_TEST
+# so the firmware-only send helpers (stream_sender, esp_log) are hidden.
+test_rv_mesh: test_rv_mesh.c $(MAIN_DIR)/rv_mesh.c $(MAIN_DIR)/rv_mesh.h $(FEATURE_STATE_SRCS) $(MAIN_DIR)/rv_radio_ops.h
+	$(CC) $(CFLAGS) -DRV_MESH_HOST_TEST=1 \
+	    test_rv_mesh.c $(MAIN_DIR)/rv_mesh.c $(FEATURE_STATE_SRCS) \
+	    -o $@ $(LDLIBS)
+
 check: all
 	./test_adaptive_controller
 	@echo ""
 	./test_rv_feature_state
+	@echo ""
+	./test_rv_mesh
 
 clean:
 	rm -f $(TESTS) *.o