unified: Swift grammar cleanup part 1

unified/AGENTS.md

@@ -5,6 +5,21 @@ This is a CodeQL extractor based on tree-sitter.
 ## Building
 To build the extractor, run `scripts/create-extractor-pack.sh`
 
+## Editing the Swift grammar
+The vendored tree-sitter-swift grammar lives at
+`extractor/tree-sitter-swift/`. After editing `grammar.js` (or any other
+grammar source), run `scripts/regenerate-grammar.sh` to:
+- regenerate `extractor/tree-sitter-swift/src/{parser.c, grammar.json,
+  node-types.json}` (and the `src/tree_sitter/*.h` headers) via
+  `tree-sitter generate`; and
+- refresh `extractor/tree-sitter-swift/node-types.yml`, the
+  human-readable companion to `src/node-types.json` produced by yeast's
+  `node_types_yaml` binary.
+
+`node-types.yml` is the recommended review surface for grammar changes —
+it shows the impact of a grammar tweak on the named node kinds, fields,
+and child types in a form much easier to read than the raw JSON.
+
 ## Testing
 - If you changed the extractor code, always rebuild it before running tests.