Add CI pipeline to validate generated schemas

Add a GH Actions workflow to validate that generated schemas are in sync with generator scripts. This will catch broken Zod schemas before publish, validate that schemas are regenerated when generator logic changes, and prevents stale/mismatched schemas.

Acceptance Criteria:

1. TypeScript compilation - Zod schemas should compile without errors
2. Schema consistency - Committed should schemas match generator output (dev MUST run npm run build after updating generators, otherwise will fail)

Workflow:

on: [pull_request, push]
steps:
  - npm ci
  - npm run build
  - git diff --exit-code  # Fail if schemas don't match
  - npx tsc --noEmit zod/index.ts  # Fail if TS errors

Start by running npm ci and npm run build, then inspect the generated schemas and zod/index.ts. Add the GitHub Actions workflow described in the issue and verify that git diff --exit-code detects stale generated files and npx tsc --noEmit zod/index.ts reports compilation errors; done means both checks pass on pushes and pull requests.