Make process diagnostics parsing more idiomatic Effect

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What Changed

• Reworked process diagnostics parsing to use Option instead of nullable sentinels for parse failures.
• Replaced the Windows diagnostics JSON.parse / ad-hoc record traversal with compiled Effect Schema decoders over Schema.UnknownFromJsonString.
• Updated the diagnostics tests to use assert from @effect/vitest and added coverage for mocked Windows process output through ChildProcessSpawner.

Why

This keeps the diagnostics code on Effect-native parsing/test seams, preserving the existing child-process abstraction while making malformed Windows process rows schema-validated and safely filtered.

Checklist

• This PR is small and focused
• I explained what changed and why

Verification:

• pnpm exec vp test run src/diagnostics/ProcessDiagnostics.test.ts from apps/server — passed (7 tests)
• pnpm exec vp check — passed (0 errors; unrelated existing React warnings)
• pnpm exec vp run typecheck — passed

  

Note

Refactor process diagnostics parsing to use Effect's Option and Schema APIs

• Replaces null-returning parse helpers (parsePositiveInt, parseNonNegativeInt, parseNumber) with Option-returning equivalents, and adds new helpers (parseInteger, trimNonEmpty, finiteNonNegativeNumberOrZero) in ProcessDiagnostics.ts.
• Introduces a WindowsProcessRecord Schema struct with typed decoders (decodeWindowsProcessJson, decodeWindowsProcessRecord) replacing raw JSON.parse for Windows process rows.
• normalizeWindowsProcessRow now returns Option<ProcessRow> and validates input via Schema, yielding Option.none for invalid records instead of silently producing bad data.
• Adds a new Windows JSON parsing test case covering field normalization, null fallbacks, invalid record filtering, and powershell invocation args; migrates all existing test assertions from expect to Effect's assert API.

^{Macroscope summarized 927c104.}