fix(agents): protect interactive REPL from external termination

[FluffyAIcode]

Summary

• install a Python SIGTERM handler that logs and ignores external termination
• add a shell supervisor that traps TERM/HUP and restarts signal-based exits (129/137/143)
• preserve explicit clean shutdown through /quit, /exit, or EOF
• document the shutdown contract

Root cause evidence

The Terminal process disappeared with zsh: terminated and no Python traceback, which means an external signal killed the REPL rather than model/gRPC logic returning an error. Memory pressure remained healthy enough and the inference services stayed online.

Tests

• verifies SIGTERM handler is installed and reports ignored termination
• verifies supervisor traps TERM/HUP and restarts signal exit codes
• focused suite — 4 passed
• full platform-neutral suite — 854 passed, 1 skipped
• Python compile, shell syntax and diff checks pass

Made with Cursor

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