Resolve the opened TAP adapter's NetCfgInstanceId to its Windows interface
index and LUID during startup, then print those values with the existing TAP
MAC/MTU diagnostics. This makes the interface identity visible before the next
metric-setting slice uses it for route protection.
The lookup failure is treated as startup failure because an opened TAP adapter
that cannot be resolved as a Windows network interface is not a good candidate
for metric or route management.
Verification note: I attempted to check `lanparty-client-win` for
`x86_64-pc-windows-msvc`, but this host still lacks the Windows C headers
needed by `ring`; the build stops at `assert.h` before the binary crate can be
typechecked for Windows.
Test Plan:
- cargo fmt --check
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
- cargo check -p lanparty-client-route --target x86_64-pc-windows-msvc
- cargo clippy -p lanparty-client-route --target x86_64-pc-windows-msvc --all-targets -- -D warnings
- git diff --check
Refs: PLAN.md
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