[Workers] Add Builds API guide with workflow examples (cloudflare#28229)

* [Workers] Add Builds API guide with workflow examples

- Document required permissions (Workers Builds Configuration + Workers Scripts Read)
- Explain Worker tag vs Worker name (external_script_id) distinction
- Add complete workflow: get Worker tag → get trigger UUID → work with builds
- Include production vs preview trigger setup with environment variables
- Add redeploy script example for refreshing build-time data
- Add end-to-end setup example from GitHub repo connection to first build
- Add troubleshooting section for common errors

* [Workers] Address bonk review feedback

- Remove editorial tone about API docs (line 37)
- Simplify troubleshooting section, link to dedicated troubleshoot page
- Replace ofetch with built-in fetch in redeploy example

* [Workers] Improve Builds API reference clarity and structure

- Clarify user-scoped token requirement and link to build token docs
- Update Worker tags section title to include external_script_id
- Rewrite trigger explanation with production/preview context
- Revert to ASCII diagrams for workflow overview
- Restructure Examples section with diagrams for each use case
- Add multiple sources for obtaining build_uuid
- Fix anchor links and API reference URLs

* 3 ASCII diagrams converted to Mermaid.

Co-authored-by: yomna-shousha <yomna-shousha@users.noreply.github.com>

* [Workers] Fix broken anchor link to trigger section

- Fix anchor link (#3-understand-triggers → #3-what-is-a-trigger)

* Fixed 3 Mermaid diagrams: fields, style

Co-authored-by: yomna-shousha <yomna-shousha@users.noreply.github.com>

* [Workers] Standardize redeploy example to curl, add SVG workflow diagrams

* [Workers] Address Greg's review comments on Builds API reference


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Co-authored-by: ask-bonk[bot] <ask-bonk[bot]@users.noreply.github.com>
Co-authored-by: yomna-shousha <yomna-shousha@users.noreply.github.com>

Author: yomna-shousha