Writing a pi-lens ast-grep Rule

Drop path: rules/ast-grep-rules/rules/<id>.yml
Same id as a built-in overrides it. Multiple rules per file: separate with ---.

Minimal template

id: no-foo-bar
language: TypeScript        # PascalCase — see languages below
severity: warning           # error | warning | hint | info — pick by evidence, see below
message: "Avoid foo.bar() — use baz() instead"
note: |
  Longer explanation / fix guidance here.
rule:
  pattern: foo.bar($ARG)

Pick the severity by the evidence behind the rule, not by feel: