feat(objc): implement class name extraction in Objective-C parser

[pleberre]

Problem

The Objective-C parser does not extract class names from Objective-C messages, reducing metadata quality for error tracking.

Context

• Referenced in commit 6917f98: "Find the Obj-C messages; todo: class name"
• Objective-C uses bracket syntax for messages: [ClassName methodName:arg]
• Class name is valuable metadata for error tracking and categorization

File Location

src/main/java/io/err0/client/languages/ObjectiveCCPPSourceCodeParse.java

Current Behavior

• Parser recognizes Objective-C messages
• Parser extracts method names
• Parser does NOT extract class names

Expected Behavior

Parser should extract class names from:

[MyClass myMethod];                  // Class: MyClass
[self someMethod];                   // Class: self (or containing class)
[[MyClass alloc] init];             // Class: MyClass
[NSLog(@"message")];                // Class: NSLog (function, not class)

Implementation Guidance

1. Look for patterns: [ClassName methodName
2. Handle nested brackets: [[Class1 method1] method2]
3. Handle self and super keywords
4. Extract class name token and store in metadata
5. Follow existing patterns from Java/Kotlin parsers for class name extraction

Test Cases Needed

Add tests in src/test/java/io/err0/client/test/Test0055ObjC.java:

• Simple message send with class name
• Nested message sends
• self and super keywords
• Mixed Objective-C and C code

Reference Files

• src/main/java/io/err0/client/languages/JavaSourceCodeParse.java (for class name extraction pattern)
• src/test/testdata/test0055/ (Objective-C test data)

Acceptance Criteria

• Class names extracted from Objective-C message syntax
• Metadata includes class name field
• Tests pass for all cases
• No regressions in existing Objective-C functionality