Add Jetpack Posts to Podcast admin page and proxy endpoint (Phase A)

[rcrdortiz]

Wires up the Jetpack-side surface for the Posts to Podcast feature:

• New "Posts to Podcast" submenu under the Jetpack admin menu, gated by Jetpack_Posts_To_Podcast_Helper::is_enabled() (delegates to Jetpack_AI_Helper for now; real Jetpack AI entitlement + credit checks land in Phase C).
• Vanilla form with three controls (window / length / voice preset) and a Generate button. Inline JS uses wp.apiFetch to POST to the local proxy, polls the job (3s for the first 30s, then 10s) until terminal state, and writes the resulting markdown script as a draft post via /wp/v2/posts. No build step needed for Phase A; Phase B can move this to a built React app under _inc/client/.
• Local wpcom/v2 proxy endpoint at posts-to-podcast (and /jobs/{id}) that forwards via Connection\Client to the wpcom-side endpoint at public-api.wordpress.com, preserving the upstream HTTP status so async-job 202/4xx/5xx mappings flow through unchanged.

The local proxy + admin page are registered in class.jetpack-admin.php alongside Jetpack_AI_Page. Three voice presets and three length presets are defined in the helper as a single source of truth shared by the form and the proxy validator.

Co-Authored-By: Claude Opus 4.7 noreply@anthropic.comFixes #

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Testing instructions

• Go to '..'

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the add/posts-to-podcast branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack add/posts-to-podcast

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/jetpack/class.jetpack-admin.php	77/240 (32.08%)	-0.41%	3 ❤️‍🩹

3 files are newly checked for coverage.

File	Coverage
projects/plugins/jetpack/_inc/lib/admin-pages/class-jetpack-posts-to-podcast-page.php	0/78 (0.00%) 💔
projects/plugins/jetpack/_inc/lib/class-jetpack-posts-to-podcast-helper.php	0/62 (0.00%) 💔
projects/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/class-wpcom-rest-api-v2-endpoint-posts-to-podcast.php	0/103 (0.00%) 💔

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