Review and acknowledge PR #1 implementation

[Copilot]

The user (@lucascherzer) implemented fixes for all automated review comments in commit a6b974b. This PR reviews and validates that implementation.

Review Completed

All 10 review comments properly addressed in a6b974b:

• Removed microvm.nix dependency - Unused flake input eliminated, reduces build closure
• Fixed TUN interface detection - Tests parse actual interface name from logs using r"TUN device created: (\S+)" (Linux-compatible)
• Fixed concurrent receiver output - stderr redirected to separate files (2> /tmp/recv_{port}.log) keeps hash files clean
• Updated documentation - AGENTS.md and vm-testing.md reference NixOS test framework, not microvm.nix
• Optimized CI workflow - Removed redundant nix flake check, consolidated builds
• Fixed module test race - Checks key existence before generation, restarts service after
• Python socket cleanup - Context managers for proper resource handling

Implementation follows project guidelines with minimal, surgical changes.

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