[hlx6] links cannot be created in browse console

[mhaack]

Steps to reproduce:

1. Open the Browse console on an hlx6 site.
2. New → Link.
3. Enter a URL and text, click Create.

Expected: a .link item is created and persists; clicking it opens the external URL.

Actual: the dialog closes and the item appears in the list, but it is never saved. After reload the link is gone; clicking it before reload fails (404). No error is surfaced.

Scope: hlx6 only. Other New types (Folder / Document / Sheet / Media) work. Link creation on non-hlx6 sites works.

[benpeter]

Root cause is in helix-api-service, not da-live.

Creating a link writes a .link file (JSON {externalUrl}) via source.save. On hlx6 this POSTs to api.aem.live/{org}/sites/{site}/source/.../x.link. The source bus only accepts a fixed extension allow-list, and .link isn't in it:

• allow-list (no .link): https://github.com/adobe/helix-api-service/blob/7f5d0fe4c381d7b87669976523132da432b38c3d/src/source/utils.js#L32-L43
• contentTypeFromExtension throws HTTP 415 for unknown ext: https://github.com/adobe/helix-api-service/blob/7f5d0fe4c381d7b87669976523132da432b38c3d/src/source/utils.js#L75-L83
• postSource calls it before storing: https://github.com/adobe/helix-api-service/blob/7f5d0fe4c381d7b87669976523132da432b38c3d/src/source/post.js#L48
• same allow-list guards folder creation: https://github.com/adobe/helix-api-service/blob/7f5d0fe4c381d7b87669976523132da432b38c3d/src/source/folder.js#L69

-> every .link save on hlx6 returns 415

Aggravator (da-live): da-new.js _handleLinkSubmit doesn't check resp.ok and daFetch doesn't throw, so the 415 fails silently — the dialog closes and an optimistic item appears, but nothing is persisted.

[benpeter]

blocked on adobe/helix-api-service#318