fix(core): avoid stopping foreign proxy port listeners

[joohw]

Summary

• Require a fresh clovapi proxy health identity check before killing a process discovered only by the configured proxy port.
• Return a clear error for foreign listeners instead of terminating them when the PID file is missing or stale.
• Add focused proxy stop lifecycle tests and bump the core dev version.

Test plan

• go test ./cmd/clovapi
• go test ./...

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