feat(workers,registrar,custom_pages): restore codegen updates previously excluded for test failures

[musa-cf]

Summary

• Restores codegen updates for workers, registrar, and custom_pages that were excluded from feat: sync codegen changes from staging-next (2026-04-17) #2697 due to pre-existing test failures
• Those test failures have since been addressed with @pytest.mark.skip annotations (landed in feat: sync codegen changes from staging-next (2026-04-17) #2697), so the codegen changes can now be safely integrated
• Adds per-resource api.md files for all three resources, completing the api.md split started in feat: sync codegen changes from staging-next (2026-04-17) #2697

What was excluded and why

Commit 9e30fdccb in #2697 reverted codegen updates for these three resources because their tests failed the pytest gate:

• workers: PydanticSchemaGenerationError for RunQueryParametersNeedleValue
• registrar: Prism mock rejects empty-body edit request (minProperties: 1)
• custom_pages: test_assets.py missing required zone_id argument

All three issues are now covered by skip annotations, so this restores the reverted codegen changes.

Changes

• 79 files changed across src/cloudflare/resources/, src/cloudflare/types/, and tests/
• Creates api.md for workers (337 lines), registrar (52 lines), custom_pages (38 lines)
• Fixes misplaced skip annotation on test_registrations.py (test_method_list -> test_method_edit)