Add Swift, Bash, YAML, and TOML tree-sitter language support

[possibilities]

Summary

• Add tree-sitter queries and language mappings for Swift, Bash, YAML, and TOML
• Swift covers classes, structs, enums, actors, extensions, protocols, typealiases, functions, and initializers
• Bash captures both function name() and name() function definition styles
• YAML extracts top-level mapping keys only (nested keys excluded) with full mapping pair spans
• TOML captures table headers (bare, dotted, quoted) and array table headers
• Quoted key/table names are normalized (wrapping quotes stripped) across TOML and YAML
• Update supported languages docs from 12 to 21

Testing

pytest tests/test_swift_symbols.py tests/test_bash_symbols.py tests/test_yaml_symbols.py tests/test_toml_symbols.py tests/test_tree_sitter_languages.py tests/test_symbol_extraction_multilang.py tests/test_tree_sitter_symbol_extractor.py -v

[possibilities]

Splitting into 4 separate PRs (one per language) for cleaner review.