fix(cli): stop advertising missing init examples

[miguel-heygen]

Summary

• document only the bundled blank example as always available
• direct users to interactive init/catalog for dynamic registry examples
• add a regression test that keeps always-available docs aligned with bundled templates

Reproduction

npx hyperframes@0.7.56 init ... --example title-card --non-interactive fails because title-card is not in the registry, despite the installed examples docs advertising it.

Test plan

• bun test packages/cli/src/docs/examples.test.ts
• bunx prettier --check packages/cli/src/docs/examples.md packages/cli/src/docs/examples.test.ts
• git diff --check

Human review required; do not self-merge.