otel: Error Handling and Sanitization

[schloerke]

Goal: Record exceptions in spans with proper sanitization for sensitive information.

Tasks

• Create shiny/otel/_errors.py with:
  • should_sanitize_errors() - Check app.sanitize_errors setting
  • sanitize_error(exception) - Replace sensitive info with generic message
  • is_silent_error(exception) - Check for SilentException, SilentCancelOutputException, etc.
  • should_record_error(exception) - Combine checks
  • maybe_sanitize_error(exception) - Apply sanitization if needed
• Update with_span_async() in shiny/otel/_span_wrappers.py:
  • Record exceptions using span.record_exception()
  • Set span status to ERROR
  • Skip silent exceptions
  • Sanitize errors when appropriate
• Ensure SafeException bypasses sanitization

Acceptance Criteria

• Exceptions recorded in spans with status code ERROR
• Silent exceptions (SilentException, etc.) not recorded
• Error messages sanitized when app.sanitize_errors=True
• SafeException messages preserved even when sanitization enabled
• Session ID included in error span attributes

Files to Create

• shiny/otel/_errors.py

Files to Modify

• shiny/otel/_span_wrappers.py