feat: integrate package name information into Signature

[pleberre]

Problem

Package name information should be integrated into method signatures for better error tracking metadata.

File Location

src/main/java/io/err0/client/core/Signature.java:32

// TODO: if we know package name, put it here...

Context

• Method signatures currently may not include full package information
• Package names provide valuable context for error tracking
• Useful for distinguishing methods with same name in different packages

Expected Behavior

When package name is known, include it in signature:

com.example.MyClass.myMethod()

Instead of just:

MyClass.myMethod()

Investigation Required

1. Where is package name extracted/stored?
2. Is package name available at signature creation time?
3. How are signatures currently formatted?
4. Would this be a breaking change to signature format?

Implementation Guidance

1. Review how signatures are constructed
2. Check if package name is available in context
3. Update signature builder to include package when available
4. Consider making this optional/configurable
5. Update signature parsing if needed

Test Cases Needed

• Signature with package name
• Signature without package name (for cases where it's not available)
• Multiple classes with same name, different packages
• Nested classes with packages

Reference Files

• src/main/java/io/err0/client/core/Signature.java
• Language parsers that extract package information
• Signature parsing/display code

Acceptance Criteria

• Package name integrated into signature when available
• TODO removed from Signature.java:32
• Tests validate package name in signatures
• Documentation updated
• Backward compatibility maintained if applicable