Remove old pattern implementation and consolidate to new bytecode VM system

- Remove src/stdlib/legacy_pattern.rs (old regex-based pattern system)
- Clean up src/stdlib/pattern.rs removing ~1000 lines of old IR parsing code
- Keep only new native functions that integrate with bytecode VM pattern system
- Update src/stdlib/pattern_test.rs with basic validation tests
- Add missing native_pattern_replace/split functions required by interpreter
- Remove legacy pattern registrations from stdlib module
- Fix TestPrograms/pattern_stdlib_test.wfl syntax for WFL function calls

This eliminates API confusion between old and new pattern systems as requested,
reducing codebase by ~2000 lines while preserving all functionality through
the new advanced natural language pattern matching system.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: claude[bot]

TestPrograms/pattern_stdlib_test.wfl

@@ -13,28 +13,35 @@ end pattern
 store test_text as "Hello 123 world 456"
 
 // Test pattern_matches function
-store word_matches as pattern_matches(test_text, word_pattern)
+store word_matches as call pattern_matches with test_text and word_pattern
 display "Word pattern matches: " with word_matches
 
-store number_matches as pattern_matches("999", number_pattern)  
+store number_matches as call pattern_matches with "999" and number_pattern  
 display "Number pattern matches '999': " with number_matches
 
 // Test pattern_find function
-store first_match as pattern_find(test_text, word_pattern)
+store first_match as call pattern_find with test_text and word_pattern
 check if first_match is not nothing:
-    display "First word found: " with first_match.matched_text
-    display "Position: " with first_match.start with " to " with first_match.end
+    store matched_text as property matched_text of first_match
+    store start_pos as property start of first_match
+    store end_pos as property end of first_match
+    display "First word found: " with matched_text
+    display "Position: " with start_pos with " to " with end_pos
 otherwise:
     display "No word found"
 end check
 
-// Test pattern_find_all function
-store all_matches as pattern_find_all(test_text, word_pattern)
+// Test pattern_find_all function  
+store all_matches as call pattern_find_all with test_text and word_pattern
 display "Found " with length of all_matches with " word matches:"
 
-count i from 0 to length of all_matches minus 1:
+store i as 0
+count from 0 to length of all_matches minus 1:
     store match_result as all_matches at i
-    display "  Match " with i with ": '" with match_result.matched_text with "' at position " with match_result.start
+    store matched_text as property matched_text of match_result
+    store start_pos as property start of match_result
+    display "  Match " with i with ": '" with matched_text with "' at position " with start_pos
+    store i as i plus 1
 end count
 
 display "Standard library pattern tests completed!"