Adds four tools that expose Deck card attachments via the MCP surface:
deck_attach_file, deck_attach_note, deck_list_attachments, and
deck_delete_attachment. The attach* variants share an existing Files
entry (or Notes-app note) with the card via OCS shareType=12 — same
mechanism the Deck UI's "Share from Files" picker uses, no file copy.
This replaces the prior workaround of appending bulky activity content
as Deck card comments: per-PR/per-event narrative now lives in NC Notes
and surfaces on the tracking card as a clickable attachment that opens
the original note in place.
Implementation reuses existing client methods (SharingClient.create_share,
DeckClient.get/delete_attachment, NotesClient.get_settings/get_note);
no new client code. _SHARE_TYPE_DECK is centralised with a CI-guard test
to prevent silent drift, and SharingClient.create_share's wire format is
pinned to what the Deck Vue source sends.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
