feat(skills-next): add cloudflare SDK references

[evanpurkhiser]

Direct LLM port of the existing cloudflare SDK skill into the skills-next per-SDK reference layout under skills-next/references/sdks/cloudflare/. This content has NOT been reviewed at all — it is a machine-generated port of the existing SDK skill, and every file should be treated as unverified.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit a645ba7. Configure here.}

[evanpurkhiser]

Automated fixes pushed addressing the review feedback on this PR:

• index.md + tracing.md: sibling links used a references/ prefix (resolving to a non-existent subdir); changed all to ./<file>.md (feature-catalog table, troubleshooting, and prose links). This was the HIGH-severity broken-link flag.
• tracing.md: the tracesSampler example returned 0 for /health while the comment said "Always trace health checks"; the comment now reads "Never trace health checks" to match (health-check routes are conventionally dropped).

Unreviewed LLM-port corrections; please verify against the SDK.