Remote clients need a stable locally administered MAC address so the relay,
gateway, DHCP lease, and LAN peers keep seeing the same tunnel identity across
runs. Requiring users to pass `--virtual-mac` made that responsibility manual.
Add a platform-neutral client identity store that loads a JSON identity file or
generates a new valid virtual MAC with OS randomness and persists it. The file
stores the MAC in the same string form shown by the CLI. The Windows client now
uses `lanparty-client-identity.json` by default while keeping `--virtual-mac` as
a manual test override.
TAP binding still remains future work; this slice only owns the client identity
that will be assigned to the TAP adapter.
Test Plan:
- cargo fmt --check
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
- git diff --check
Refs: PLAN.md MAC identity
lanparty-client-win now has a real command-line surface for the relay-facing
client session. It accepts the relay address, expected TLS server name, pinned
DER relay certificate, room code, virtual TAP MAC, and advertised datagram
budget, then connects through lanparty-client-core as role = client.
The binary reports the assigned peer id, room id, and effective TAP MTU from the
welcome response, then waits for Ctrl-C. TAP adapter binding and Windows route
pinning remain future slices, but the executable now exercises the real relay
control-plane path instead of the starter placeholder.
Test Plan:
- cargo fmt --check
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
Refs: PLAN.md Windows client relay connection
ddidderr
