fix(docker): ensure container exits instantly without hanging

[jamesbrink]

• Add tini as init system for proper signal forwarding and zombie reaping
• Use mcp_nixos.run wrapper for aggressive process termination
• Set low timeout values via environment variables
• Enable cleanup of orphan processes
• Add explicit STOPSIGNAL for Docker to use

🤖 Generated with Claude Code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.10%. Comparing base (24f8c10) to head (44fa188).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #4      +/-   ##
==========================================
- Coverage   71.14%   71.10%   -0.05%     
==========================================
  Files          32       32              
  Lines        4329     4329              
==========================================
- Hits         3080     3078       -2     
- Misses       1249     1251       +2     

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