feat: add example validation CI script (Closes #94)

[panditdhamdhere]

Summary

• Harden scripts/check-examples.mts with clear Zod path/message error output (--verbose)
• Add pnpm test:examples covering valid and invalid example fixtures
• Add CI workflow .github/workflows/check-examples.yml
• Document when to run validation in docs/examples.md and link from README

Closes #94

Issue scope

• Example validation script is added
• Examples are validated against shared schemas where applicable
• Invalid examples produce clear error output
• Tests cover valid and invalid example files
• Package scripts include the validation command
• Documentation explains when to run validation

Affected packages / apps

• apps/web
• packages/types
• packages/config
• packages/fixtures
• packages/validators
• packages/stellar-kit
• packages/anchor-utils
• contracts/treasury-escrow
• docs/
• Other: scripts/check-examples.mts, scripts/check-examples.test.ts, .github/workflows/check-examples.yml, package.json, examples/, README.md, apps/web/app/docs/page.tsx

Testing performed

• pnpm check:examples -- --verbose
• pnpm test:examples

Screenshots / recordings

N/A

Security impact

• This PR touches secret handling, callback URLs, network selection, or contract admin/authorization logic
• No security-relevant surface touched

Documentation impact

• Docs under /docs updated for this change
• README updated (new package, script, or workflow)
• No user-facing behaviour changed — no docs update needed

[El-swaggerito]

\nGitHub has not finished calculating whether this PR can be merged cleanly.\n\nThe auto-merge automation will skip this PR for now. Re-run the automation later.

[El-swaggerito]

\nThis PR is currently blocked by merge conflicts.\n\nPlease update the branch with the latest main branch and resolve the conflicts before it can be merged.

[panditdhamdhere]

kindly check now.