chore(repo): rename rust-port/wifi-densepose-rs → v2/ (flatten to one level) (#427)

The Rust port lived two directories deep (rust-port/wifi-densepose-rs/)
without any sibling under rust-port/ that warranted the extra level.
Move the whole workspace up to v2/ to match v1/ (Python) at the same
depth and shorten every cd / build command across the repo.

git mv preserves history for all tracked files. 60 files updated for
path references (CI workflows, ADRs, docs, scripts, READMEs, internal
.claude-flow state). Two manual fixes for relative-cd paths in
CLAUDE.md and ADR-043 that became wrong after the depth change
(cd ../.. → cd ..).

Validated:
- cargo check --workspace --no-default-features → clean (after target/
  nuke; the gitignored target/ was carried by the OS rename and had
  hard-coded old paths in build scripts)
- cargo test --workspace --no-default-features → 1,539 passed, 0 failed,
  8 ignored (same totals as pre-rename)
- ESP32-S3 on COM7 → still streaming live CSI (cb #40300, RSSI -64 dBm)

After-merge follow-up: contributors should `rm -rf v2/target` once and
let cargo regenerate from the new path.

.github/workflows/ci.yml

@@ -79,13 +79,13 @@ jobs:
         path: |
           ~/.cargo/registry
           ~/.cargo/git
-          rust-port/wifi-densepose-rs/target
-        key: ${{ runner.os }}-cargo-${{ hashFiles('rust-port/wifi-densepose-rs/Cargo.lock') }}
+          v2/target
+        key: ${{ runner.os }}-cargo-${{ hashFiles('v2/Cargo.lock') }}
         restore-keys: |
           ${{ runner.os }}-cargo-
 
     - name: Run Rust tests
-      working-directory: rust-port/wifi-densepose-rs
+      working-directory: v2
       run: cargo test --workspace --no-default-features
 
   # Unit and Integration Tests