Compiler architecture

A classic multi-pass pipeline (each stage a module under src/); src/driver.rs runs the shared front-end (read → lex → parse → resolve imports → typecheck) for all CLI commands and renders any failure through src/diagnostic.rs (the rustc-style path:line:col reporter described under Error messages).

1. Lexer — src/lexer/ (logos), Lexer::tokenize(&str).
2. Parser — src/parser/ast_parser.rs, hand-written recursive descent, parse(&tokens).
3. AST — src/ast/nodes.rs.
4. Type checker — src/typechecker/checker.rs plus its per-area child modules.
5. Code generator — src/codegen/generator.rs plus its per-area child modules (inkwell, LLVM 22) → LLVM IR.
6. Runtime intrinsics — src/runtime/ (__write_bytes, grapheme counting, GC glue), packaged as libquilon_rt.
7. LLVM — quilon build emits an object in-process and links libquilon_rt into a native binary; quilon run uses an in-process JIT.

See CLAUDE.md for contributor guidance.