Use Effect idioms in diagnostics and keyed worker

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What Changed

• Updated the process resource monitor to represent timing policy with Duration, repeat sampling with Schedule.spaced, and store/report the latest sampling error as Option.
• Reworked KeyedCoalescingWorker queue state to use Option instead of null/undefined sentinels, preserving undefined values as valid queued work.
• Switched touched tests to @effect/vitest assert style and added focused coverage for the new Option-backed paths.

Why

These are small Effect idiom improvements that make monitor timing easier to test with Effect primitives and remove sentinel values from queue state, including fixing the edge case where an explicitly undefined queued value would be dropped.

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

Use Effect idioms for Option types and scheduling in diagnostics and keyed worker

• Replaces null/undefined sentinel values with Option types for lastError in ProcessResourceMonitor and for key values in KeyedCoalescingWorker, fixing cases where undefined values were silently treated as absent.
• Replaces the manual forever loop in ProcessResourceMonitor with Effect.repeat(Schedule.spaced(SAMPLE_INTERVAL)) for cleaner scheduling.
• Clamps window and bucket durations to a minimum of 1 second in aggregateProcessResourceHistory via Duration.max.
• Updates tests in both modules to use @effect/vitest assert API and adds coverage for undefined enqueue and Option-mapped sampling errors.
• Behavioral Change: KeyedCoalescingWorker now processes keys whose latest value is undefined rather than skipping them; ProcessResourceMonitor now clamps sub-1s window/bucket inputs.

^{Macroscope summarized bd57f3b.}