fix(wasm-edge): sanitize non-finite host floats at the WASM↔host frame boundary (ruvnet#1102)

Closing beyond-SOTA security review of wifi-densepose-wasm-edge (ADR-040,
~70 edge modules). The two WASM↔host boundaries (lib.rs::on_frame/on_timer
and bin/ghost_hunter.rs::on_frame) read raw IEEE-754 f32 from the csi_get_*
imports with no finiteness check — the crate had zero is_finite/is_nan
guards and its clamp helpers propagate NaN. A single non-finite host value
latches NaN into long-lived per-module accumulators (EMA / Welford / phasor
sums / anomaly baselines), after which detectors fail degraded (stuck gate
state, silently-disabled checks) — silent corruption, not a crash.

Add sanitize_host_f32() (non-finite -> 0.0, core-only for no_std) applied at
every host_get_* float read: one chokepoint covering all downstream modules,
mirroring the existing M-01 negative-n_subcarriers boundary clamp. LOW /
defense-in-depth (the Tier-2 DSP firmware supplies the imports, a semi-trusted
boundary).

Pinned by boundary_tests::{sanitize_passes_finite_values_through,
sanitize_maps_non_finite_to_zero,
coherence_monitor_nan_latches_without_sanitize_but_not_with} — the last
asserts on the current CoherenceMonitor that a raw NaN frame latches the
smoothed score while the sanitized path stays finite.

Other review dimensions attested clean with evidence (see CHANGELOG): no
hot-path panics (all unwrap/expect are test-only or std-gated RVF builder),
all bounds min()-clamped, all index-by-cast const-bounded or guarded, no
leaking closures (no move||/forget/leak), no secrets.

Verified: host `cargo test --features std,medical-experimental` 672 passed /
0 failed (+3 new tests); all three wasm32-unknown-unknown release artifacts
build clean (lib default no_std/panic=abort, ghost_hunter standalone-bin,
medical-experimental); Python proof VERDICT PASS, hash unchanged.

Author: ruvnet