feat: Add 6 new languages to codebase analysis system (C#, Go, Rust, Java, Ruby, PHP)

Expands language support from 3 to 9 languages across entire codebase scraping system.

**New Languages Added:**
- C# (Unity/.NET support) - classes, methods, properties, async/await, XML docs
- Go - structs, functions, methods with receivers, multiple return values
- Rust - structs, functions, async functions, impl blocks
- Java - classes, methods, inheritance, interfaces, generics
- Ruby - classes, methods, inheritance, predicate methods
- PHP - classes, methods, namespaces, inheritance

**Code Analysis (code_analyzer.py):**
- Added 6 new language analyzers (~1000 lines)
- Regex-based parsers inspired by official language specs
- Extract classes, functions, signatures, async detection
- Comprehensive comment extraction for all languages

**Dependency Analysis (dependency_analyzer.py):**
- Added 6 new import extractors (~300 lines)
- C#: using statements, static using, aliases
- Go: import blocks, aliases
- Rust: use statements, curly braces, crate/super
- Java: import statements, static imports, wildcards
- Ruby: require, require_relative, load
- PHP: require/include, namespace use

**File Extensions (codebase_scraper.py):**
- Added mappings: .cs, .go, .rs, .java, .rb, .php

**Test Coverage:**
- Added 24 new tests for 6 languages (4 tests each)
- Added 19 dependency analyzer tests
- Added 6 language detection tests
- Total: 118 tests, 100% passing ✅

**Credits:**
- Regex patterns based on official language specifications:
  - Microsoft C# Language Specification
  - Go Language Specification
  - Rust Language Reference
  - Oracle Java Language Specification
  - Ruby Documentation
  - PHP Language Reference
- NetworkX for graph algorithms

**Issues Resolved:**
- Closes #166 (C# support request)
- Closes #140 (E1.7 MCP tool scrape_codebase)

**Test Results:**
- test_code_analyzer.py: 54 tests passing
- test_dependency_analyzer.py: 43 tests passing
- test_codebase_scraper.py: 21 tests passing
- Total execution: ~0.41s

🚀 Generated with Claude Code
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/skill_seekers/cli/codebase_scraper.py

@@ -12,10 +12,16 @@ Usage:
 
 Features:
     - File tree walking with .gitignore support
-    - Multi-language code analysis (Python, JavaScript, C++)
+    - Multi-language code analysis (9 languages: Python, JavaScript/TypeScript, C/C++, C#, Go, Rust, Java, Ruby, PHP)
     - API reference generation
     - Comment extraction
+    - Dependency graph analysis
     - Configurable depth levels
+
+Credits:
+    - Language parsing patterns inspired by official language specifications
+    - NetworkX for dependency graph analysis: https://networkx.org/
+    - pathspec for .gitignore support: https://pypi.org/project/pathspec/
 """
 
 import os
@@ -61,6 +67,13 @@ LANGUAGE_EXTENSIONS = {
     '.h': 'C++',
     '.hpp': 'C++',
     '.hxx': 'C++',
+    '.c': 'C',
+    '.cs': 'C#',
+    '.go': 'Go',
+    '.rs': 'Rust',
+    '.java': 'Java',
+    '.rb': 'Ruby',
+    '.php': 'PHP',
 }
 
 # Default directories to exclude