zlint

Author a new zlint lint rule end-to-end - scaffold the rule file, implement the runOnNode/runOnSymbol/runOnce hooks, write RuleTester pass/fail/fix cases with snapshot output, and regenerate docs and schema. Use when adding a lint rule, implementing a rule listed on the rule ideas board, renaming or recategorizing an existing rule, or when the user mentions creating, adding, or scaffolding a rule in this repo.