Use Effect Schema decoding in diagnostics parsers

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What Changed

• Replaced ad-hoc diagnostics JSON.parse handling with Effect Schema decoding for trace NDJSON records and Windows process JSON output.
• Added targeted coverage for malformed trace input and Windows process JSON null/invalid rows.
• Switched the touched ProcessDiagnostics tests from expect to assert and added an explicit tagged-error guard for narrowing.

Why

This keeps diagnostics parsing more idiomatic Effect: JSON inputs now flow through Schema decoding, malformed input remains safely ignored/countable, and tests use the preferred @effect/vitest assertion style.

Checklist

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

  

Note

Replace JSON.parse with Effect Schema decoding in diagnostics parsers

• Replaces JSON.parse try/catch blocks in TraceDiagnostics.ts and ProcessDiagnostics.ts with Schema.decodeUnknownOption-based decoders.
• Adds WindowsProcessRecord, TraceRecord, and TraceEventRecord Effect Schema structs to validate parsed data; invalid records are silently dropped rather than causing exceptions.
• Exports parseWindowsProcessRows for external use.
• Behavioral Change: non-conforming Windows process records and trace lines that previously may have passed loose typeof checks are now excluded from results.

^{Macroscope summarized edcebbd.}