feat(attr): add attribute change event system

[SunYanbox]

Summary

Add an AttributeChanged event to Attr<TKey, TModId, TValue> that fires whenever a modifier mutation actually changes the computed attribute value.

Changes

Event System (d507ba2)

• New AttributeChanged event — fires on every effective mutation (SetModifier, RemoveModifier, RemoveAllModifiers, Clear)
• New AttrChangeType enum — SetModifier, RemoveModifier, RemoveAll, Clear
• New AttrChangedEventArgs<TKey, TValue> class — exposes Key, ChangeType, NewValue
• Safe invocation — events fire outside per-key and global locks to prevent deadlocks when handlers call back into the attribute
• Isolated subscribers — uses GetInvocationList() so one subscriber's exception does not block others
• Cache-aware — cache is invalidated before the event fires, so GetValue inside handlers returns fresh data
• No false events — setting a modifier to the same value remains a no-op and does not fire

Documentation Update (5697c0e)

• Updated both English and Chinese READMEs to document the new APIs
• Added event usage examples to Quick Start sections
• Documented event safety guarantees and thread-safety implications

Testing

• 312-line MSTest test suite (AttrEventTest.cs) covering all event scenarios
• Tests verify correct invocation, isolation, no-op behavior, and lock safety
• All existing tests continue to pass

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[SunYanbox]

Updates between 988cb96 → 650796e

Three new commits were added to extend the event system with logging support and finalize documentation:

011d0d4 — feat(attr): add logging support to attribute change event system

• Added Microsoft.Extensions.Logging dependency (Logging, Abstractions, Console)
• Added AttrLoggingConfiguration — static helper that creates an ILoggerFactory from environment variables (GAMEATTR_LOG_CONSOLE, GAMEATTR_LOG_FILE)
• Added a lightweight file logger provider writing to gameattr.log
• Added Attr(ILogger<...>) constructor overload
• Subscriber exceptions in RaiseAttributeChanged are now logged as warnings instead of swallowed silently

3adb185 — test: add comprehensive unit test coverage for logging configuration

• 163-line MSTest suite (AttrLoggingConfigurationTest.cs) covering console output, file output, disabled console, and invalid environment variable values

650796e — docs(readme): add logging configuration documentation

• Documented AttrLoggingConfiguration.CreateLoggerFactory() with environment variable reference table
• Added code example for configuring and passing a logger to the constructor
• Mentioned logging support in the Features list
• Updated both English and Chinese READMEs