feat(client): print runtime diagnostics snapshots

The client now builds ClientDiagnostics snapshots from the connected session,
known TAP state, route-pinning status, and tunnel counters. Windows prints one
snapshot after TAP and relay-route setup, then repeats snapshots while bridging
so frame/datagram counters and drops are visible during manual phase-1 tests.

Non-Windows builds print the same relay and QUIC diagnostics with TAP fields
marked unknown before waiting for Ctrl-C. TAP IP remains unknown until a later
Windows adapter IP inspection slice wires that source of truth.

Test Plan:
- cargo fmt --check
- cargo test -p lanparty-client-win
- cargo clippy -p lanparty-client-win --all-targets -- -D warnings
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
- git diff --check

Refs: PLAN.md

crates/lanparty-client-win/Cargo.toml

@@ -8,6 +8,7 @@ anyhow.workspace = true
 clap.workspace = true
 lanparty-client-core = { path = "../lanparty-client-core" }
 lanparty-ctrl = { path = "../lanparty-ctrl" }
+lanparty-obs = { path = "../lanparty-obs" }
 lanparty-proto = { path = "../lanparty-proto" }
 tokio.workspace = true