Refactor preview port scanner Effect patterns

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What Changed

• Added an Effect Context.Reference for the preview port scanner platform, so tests can provide win32 through a layer instead of mutating process.platform.
• Replaced command-scan null fallbacks with Effect.option/Option handling and switched timeout constants to Duration.seconds values.
• Updated the port scanner test file to use @effect/vitest assertions in the touched coverage.

Why

This keeps the preview port scanner more idiomatic and testable with Effect: runtime platform is now injectable via context, expected command failures are modeled as optional fallbacks, and tests no longer monkey-patch global Node state.

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:

• pnpm --filter t3 exec vp test run src/preview/PortScanner.test.ts (17 tests passed)
• pnpm exec vp run typecheck
• pnpm exec vp check (0 errors, 11 existing warnings)

  

Note

Refactor PortScanner to inject platform context and use Effect-native patterns

• Introduces CurrentPlatform as a Context.Reference in PortScanner.ts, replacing direct reads of process.platform so the Windows code path can be injected in tests without monkey-patching.
• Replaces null-based fallback control flow with Effect.option and Option.isSome checks in PortDiscovery.make.
• Replaces numeric millisecond timeout constants with Duration-based constants (LSOF_TIMEOUT, WINDOWS_LISTENER_TIMEOUT).
• Migrates PortScanner.test.ts assertions from expect to @effect/vitest assert APIs, updates the mock ProcessRunner to return a typed ProcessSpawnError, and supplies CurrentPlatform via the test layer.

^{Macroscope summarized ba5fd84.}

[github-actions]

🚀 Expo continuous deployment is ready!

• Project → t3-code
• Platforms → android, ios
• Scheme → t3code-preview

	🤖 Android	🍎 iOS
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Build Details	Build Permalink Details Distribution: INTERNAL Build profile: preview:dev Runtime version: ae17d94b35f91f9c608a63dadbc3ddd9f4ba056e App version: 0.1.0 Git commit: 817bb447f46bb6025ac1ab7864fd54273ee18150	Build Permalink Details Distribution: INTERNAL Build profile: preview:dev Runtime version: 313e506a7f15a9c3f15b01d787d68a12382432bf App version: 0.1.0 Git commit: 817bb447f46bb6025ac1ab7864fd54273ee18150
Update Details	Update Permalink Details Branch: pr-3082 Runtime version: ae17d94b35f91f9c608a63dadbc3ddd9f4ba056e Git commit: 817bb447f46bb6025ac1ab7864fd54273ee18150	Update Permalink Details Branch: pr-3082 Runtime version: 313e506a7f15a9c3f15b01d787d68a12382432bf Git commit: 817bb447f46bb6025ac1ab7864fd54273ee18150
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