Add connection timeout tests

[quiloos39]

Summary

• Add 9 tests verifying SSH connection and command execution timeout behavior
• Covers outer connection timeout, command timeout with partial output, readyTimeout derivation, settled-flag guard, ready-before-timeout race, broken-pipe detection, stale connection rejection, default values, and connection replacement cleanup

Test plan

• Run node --import tsx --test tests/connection-timeout.test.ts and verify all 9 tests pass
• Verify timeout logic matches src/tools/connect.ts and src/tools/execute.ts patterns