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.

docs/adr/ADR-043-sensing-server-ui-api-completion.md

@@ -289,7 +289,7 @@ Startup creates `data/models/` and `data/recordings/` directories and populates
 
 ```bash
 # 1. Start sensing server with auto source (simulated fallback)
-cd rust-port/wifi-densepose-rs
+cd v2
 cargo run -p wifi-densepose-sensing-server -- --http-port 3000 --source auto
 
 # 2. Verify model endpoints return 200
@@ -312,11 +312,11 @@ curl -s http://localhost:3000/api/v1/models/lora/profiles | jq '.'
 # Navigate to http://localhost:3000/ui/
 
 # 7. Run mobile tests
-cd ../../ui/mobile
+cd ../ui/mobile
 npx jest --no-coverage
 
 # 8. Run Rust workspace tests (must pass, 1031+ tests)
-cd ../../rust-port/wifi-densepose-rs
+cd ../../v2
 cargo test --workspace --no-default-features
 ```