v0.7.22

feat: tree-sitter AST-aware chunking for code search

Replace line-based chunking with tree-sitter AST parsing (like seemb).
Chunks are now syntactically meaningful: whole functions, classes, structs.
10 languages supported: rust, python, javascript, typescript, go, c, cpp,
java, ruby, c-sharp. Falls back to line-based for unsupported languages.

Bump version to 0.2.0.