fix: harden MERIDIAN modules from code review + security audit

- domain.rs: atomic instance counter for unique Linear weight seeds (C3)
- rapid_adapt.rs: adapt() returns Result instead of panicking (C5),
  bounded calibration buffer with max_buffer_frames cap (F1-HIGH),
  validate lora_rank >= 1 (F10)
- geometry.rs: 24-bit PRNG precision matching f32 mantissa (C2)
- virtual_aug.rs: guard against room_scale=0 division-by-zero (F6)
- signal/lib.rs: re-export AmplitudeStats from hardware_norm (W1)
- train/lib.rs: crate-root re-exports for all MERIDIAN types (W2)

All 201 tests pass (96 unit + 24 integration + 18 subcarrier +
10 metrics + 7 doctests + 105 signal + 10 validation + 1 signal doctest).

Co-Authored-By: claude-flow <ruv@ruv.net>

rust-port/wifi-densepose-rs/crates/wifi-densepose-signal/src/lib.rs

@@ -56,7 +56,7 @@ pub use motion::{
     HumanDetectionResult, MotionAnalysis, MotionDetector, MotionDetectorConfig, MotionScore,
 };
 pub use hardware_norm::{
-    CanonicalCsiFrame, HardwareNormError, HardwareNormalizer, HardwareType,
+    AmplitudeStats, CanonicalCsiFrame, HardwareNormError, HardwareNormalizer, HardwareType,
 };
 pub use phase_sanitizer::{
     PhaseSanitizationError, PhaseSanitizer, PhaseSanitizerConfig, UnwrappingMethod,