fix(vm): categorize user or server side errors

[TheodoreSpeaks]

Summary

Brief description of what this PR does and why.

Fixes #(issue)

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation
• Other: ___________

Testing

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Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Apr 24, 2026 0:30am

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PR Summary

Medium Risk
Changes how isolated-vm and preview APIs classify and surface sandbox errors (422 vs 500), which can affect client behavior and monitoring/alerting if misclassified.

Overview
Improves sandbox error categorization by introducing IsolatedVMError.isSystemError and using it in runSandboxTask to throw a dedicated SandboxUserCodeError for user-caused failures while treating infrastructure/pool/task failures as system errors.

Document preview endpoints now catch SandboxUserCodeError and return 422 with { error, errorName } (and warn-level logging) instead of always returning 500; tests for PDF/PPTX/DOCX previews were updated to cover the new 422 behavior.

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