ci: gate every example workspace error-free — pds doc over samples/* and model/

[shockwave-bot]

Found during #58 review.

Gap

• banking sample cleanliness is CI-gated (operators-constants.spec.ts problems-badge assertion).
• acme-tickets, acme-payments, model/ have no error-free gate — lang: mandatory return types — every callable declares : Type, void explicit #58's sample sweep was trusted only via a manual pds doc run.

Ask

• CI step: pds doc over web-ide/src/lib/samples/* + model/; fail on any error-severity diagnostic.
• Keeps the CLAUDE.md contract ("every worked example compiling and exemplary") measured, not assumed.

refs #58