#214 Attach shared files into the Messenger composer

[Anonymous]

Originally created by: kristofferR

The final hop for both platforms is to turn a native, validated share payload into unsent attachments in the open Messenger conversation.

Implemented design

• share-intake.ts installs the native-only window.__carrierShareMedia hook, validates the payload again, decodes each entry into a File, and targets only the visible conversation composer.
• Delivery first uses Messenger's paste path, then a drop fallback. Success requires the exact transfer object to be inspected and the event to be cancelled. If a handler inspected the payload without acknowledging it, Carrier reports an uncertain failure and never retries into duplicate attachments.
• If no composer exists, the share waits for up to two minutes and shows a prompt to open a conversation. Additional shares merge within the advertised count cap instead of silently replacing pending files.
• Pure count, aggregate encoded-size, UTF-8 name, MIME, freshness, and transfer-acknowledgement logic lives under inject/src/messenger/lib/ with focused Bun tests.

Verification

Verified with a PNG from the real Finder share sheet. Carrier came forward and the filename plus remove control rendered in the open conversation's composer; the unsent attachment was removed after the check.

Implemented by [#220]. The same delivery path is intended for Windows [#216]. Part of [#217].

[Anonymous]

Originally posted by: kristofferR

Completed by [#220]. A Finder-shared PNG was verified as a rendered, unsent attachment in Messenger's composer.

[Anonymous]

Ticket changed by: kristofferR

• status: open --> closed