Use more idiomatic Effect patterns in server runtime paths

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What Changed

• Changed the managed endpoint runtime service API and internal refs to use Option for desired/active runtime config instead of nullable values.
• Kept JSON/HTTP null at the boundary and convert it to Option before invoking the service.
• Updated orchestration integration harness polling to use Duration, Schedule, and a structured tagged retry signal instead of raw millisecond retry math and a string sentinel.
• Updated the managed endpoint runtime tests to pass Option values and use assert from @effect/vitest.

Why

These are small server-side idiom improvements that make state and polling policies easier to test and reason about with Effect primitives while preserving existing behavior.

UI Changes

N/A - no UI changes.

Checklist

• This PR is small and focused
• I explained what changed and why
• UI screenshots are not applicable
• Animation/interaction video is not applicable

  

Note

Replace null/undefined patterns with Effect Option in server runtime paths

• Refactors ManagedEndpointRuntime to use Option throughout: applyConfig now accepts Option-wrapped configs, internal refs use Option.none, and stopConnector uses Option.match.
• Updates OrchestrationEngineHarness to replace string sentinel RETRY_SIGNAL with a tagged WaitForRetrySignal error and accept Duration.Input instead of millisecond numbers for timeouts.
• Updates call sites in http.ts, server.test.ts, and ManagedEndpointRuntime.test.ts to pass Option-wrapped values and use @effect/vitest assertions.
• Behavioral Change: applyConfig callers must now wrap configs in Option.some(...) or pass Option.none(); raw objects and null are no longer accepted.

^{Macroscope summarized 66d9fcf.}