Fix ClassCastException in MagicNumberDiagnostic with soft error handling

[Copilot]

The MagicNumberDiagnostic.configure() method was throwing a ClassCastException when the configuration system provided an ArrayList instead of a String for the authorizedNumbers parameter. This caused the entire diagnostic system to fail during bean creation.

Root Cause

The issue occurred at line 72 in MagicNumberDiagnostic.java:

var authorizedNumbersString =
  (String) configuration.getOrDefault("authorizedNumbers", DEFAULT_AUTHORIZED_NUMBERS);

When the configuration contained an ArrayList (e.g., ["-1", "0", "1"]), the unsafe cast to String failed with:

ClassCastException: class java.util.ArrayList cannot be cast to class java.lang.String

Solution

Implemented robust configuration handling with soft error recovery:

1. Type-safe configuration parsing: Added proper type checking to handle both String and List formats
2. Soft error handling: Invalid configurations now log warnings and fall back to defaults instead of crashing
3. Comprehensive error recovery: Try-catch block ensures no exceptions propagate from configuration
4. Enhanced logging: Added detailed warning messages for troubleshooting invalid configurations

Changes Made

• Added @Slf4j annotation and logging imports
• Replaced unsafe cast with instanceof type checking
• Added support for both String ("-1,0,1") and List (["-1","0","1"]) formats
• Added comprehensive error handling with fallback to default values
• Added warning logs for invalid configuration types

Testing

• Added test case testConfigureWithArrayListShouldNotThrowClassCastException() to verify ArrayList handling
• Added test case testConfigureWithInvalidTypeShouldUseDefaults() to verify error recovery
• Verified all existing MagicNumberDiagnostic tests continue to pass
• Confirmed warning logs are properly generated for invalid configurations

The fix ensures diagnostic configuration errors result in warning messages and graceful fallbacks rather than application crashes, as requested by @nixel2007.

Fixes #3485.

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