fix: update Mihomo TUN key serialization

[paiwoo]

Summary

• update the FlClash Mihomo submodule so tun.auto-detect-interface is serialized using its valid Mihomo key

Dependency

• Depends on fix: preserve TUN auto-detect key in JSON Clash.Meta#4.

Issue

Fixes #1992.

Verification

• The submodule adds a focused JSON serialization regression test.
• The local Go 1.25.0 runtime fails before project packages compile because of duplicate Swiss-map symbols; upstream CI should run the test.