feat(rvcsi): rvcsi-core + napi-c Nexmon shim + crate skeletons (ADR-095/096)

First implementation milestone for the rvCSI edge RF sensing runtime:

- rvcsi-core — the foundation: CsiFrame/CsiWindow/CsiEvent normalized schema,
  ValidationStatus, AdapterProfile, CsiSource plugin trait, id newtypes +
  IdGenerator, RvcsiError, and the validate_frame pipeline (length/finiteness/
  subcarrier/RSSI/monotonicity hard checks + multiplicative quality scoring →
  Accepted/Degraded/Recovered/Rejected). 29 unit tests, forbid(unsafe_code).
- rvcsi-adapter-nexmon — the napi-c boundary: native/rvcsi_nexmon_shim.{c,h}
  (the only C in the runtime, allocation-free, bounds-checked, parses/writes a
  byte-defined "rvCSI Nexmon record" — a normalized superset of the nexmon_csi
  UDP payload), compiled via build.rs + cc, wrapped by a documented ffi module
  and a NexmonAdapter implementing CsiSource. 9 tests round-tripping through C.
- Workspace registration in v2/Cargo.toml (8 new members + napi/cc workspace
  deps) and compiling skeletons for rvcsi-dsp, rvcsi-events, rvcsi-adapter-file,
  rvcsi-ruvector, rvcsi-node (napi-rs cdylib + build.rs napi_build::setup) and
  rvcsi-cli (`rvcsi` binary) — to be filled in by the implementation swarm.

cargo build -p rvcsi-core -p rvcsi-adapter-nexmon -p rvcsi-node -p rvcsi-cli: OK
cargo test  -p rvcsi-core -p rvcsi-adapter-nexmon: 38 passed, 0 failed

https://claude.ai/code/session_01CdYAPvRTjcch6YrYf42n1z

v2/crates/rvcsi-node/src/lib.rs

@@ -0,0 +1,22 @@
+//! # rvCSI Node.js bindings — napi-rs (skeleton; completed during integration)
+//!
+//! The safe TypeScript-facing surface over the rvCSI Rust runtime
+//! (ADR-095 D3/D4, ADR-096). Nothing here exposes raw pointers; every value
+//! that crosses the boundary is a validated/normalized struct or a JSON string.
+
+#![deny(clippy::all)]
+
+#[macro_use]
+extern crate napi_derive;
+
+/// rvCSI runtime version (the workspace crate version).
+#[napi]
+pub fn rvcsi_version() -> String {
+    env!("CARGO_PKG_VERSION").to_string()
+}
+
+/// ABI version of the linked napi-c Nexmon shim (`major << 16 | minor`).
+#[napi]
+pub fn nexmon_shim_abi_version() -> u32 {
+    rvcsi_adapter_nexmon::shim_abi_version()
+}