Use Effect Duration policies in SSH readiness

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What Changed

• Replaced SSH command and tunnel readiness timeout options with Duration.Input values.
• Centralized SSH readiness, probe, and shutdown policy constants as Duration values.
• Swapped nullable readiness probe state for Option while preserving millisecond diagnostic fields.
• Updated SSH Effect-vitest coverage to exercise the duration-based API.

Why

This makes the SSH path more idiomatic Effect by keeping timing policies in effect/Duration and using Option for optional state. Millisecond conversion now happens only at integration/diagnostic boundaries such as remote script placeholders and log fields.

UI Changes

None.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

  

Note

Replace millisecond number options with Duration inputs in SSH readiness checks

• Replaces timeoutMs, intervalMs, and probeTimeoutMs number options with timeout, interval, and probeTimeout accepting Duration.Input in waitForHttpReady (tunnel.ts) and runSshCommand (command.ts).
• Internal millisecond constants (e.g. SSH_READY_TIMEOUT_MS) are replaced with Duration constants; effective timeout values are unchanged.
• Scripts built by buildRemoteLaunchScript still receive millisecond strings, now derived via Duration.toMillis.
• Risk: Breaking API change — callers of runSshCommand and waitForHttpReady must update from numeric millisecond options to Duration.Input options.

^{Macroscope summarized 4316922.}