Use idiomatic Effect services for orchestration and open launching

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What Changed

• Use DateTime.now / DateTime.formatIso for orchestration-generated timestamps.
• Use Random.nextUUIDv4 for orchestration event IDs instead of crypto.randomUUID().
• Launch editors through Effect ChildProcessSpawner instead of native node:child_process.spawn.
• Added focused deterministic tests with TestClock, deterministic Random.Random, and a mocked child process spawner.

Why

This keeps orchestration timestamps and IDs testable through Effect services, and makes detached editor launching mockable without running real child processes in unit tests.

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

Verification:

• bun fmt
• bun lint
• bun typecheck
• bun run test src/open.test.ts src/orchestration/decider.clock.test.ts
• bun run test src/orchestration/decider.clock.test.ts

  

Note

Use Effect services for time, UUID generation, and process spawning in orchestration and open launching

• Replaces new Date().toISOString() and crypto.randomUUID() in decider.ts with Effect DateTime and Random.nextUUIDv4, making timestamps and event IDs controllable via Effect layers in tests.
• Refactors launchDetached in open.ts to use the Effect ChildProcessSpawner service instead of Node's child_process.spawn directly, with explicit stdio ignore and shell mode on Windows.
• Updates tests in open.test.ts and decider.clock.test.ts to inject mock Effect services and assert deterministic output.
• Behavioral Change: openBrowser now returns void instead of the underlying library's return value.

^{Macroscope summarized 328bf03. (Automatic summaries will resume when PR exits draft mode or review begins).}