feat: add semantic mode checks for z.input/z.output

[greyllmmoder]

Summary

• add --semantics off|input|output|both to zodrift check
• add semantic issue type (semantic_mismatch) and include semantic counts in reports
• implement semantic checker using TypeScript probe files for z.input<typeof Schema> and z.output<typeof Schema>
• wire semantic checks into pretty/json/sarif reporters
• add tests covering input mismatch, output mismatch (preprocess case), and matching schema/type pass case
• update README and docs (docs/check.md, docs/ci.md) with semantic CI usage

Testing

• npm run typecheck
• npm run build
• npm test
• npm run dev -- check --pattern "examples/**/*.ts" --semantics both