POST /v2/social/posts

Creates a community post containing text and/or structured token, post or position attachments. Send a position with chain_id and address, without snapshot, to capture the authenticated owner's current Codex holding as provider_reported. Caller-supplied snapshots remain author_claimed. Parent and attachment inserts are atomic. Unavailable or incomplete position observations return 503 position_snapshot_unavailable with no post written. Missing holdings or invisible source references return 404 attachment_reference_not_found. Approved post media_ids may accompany text and structured attachments or create a media-only post; publish_to_x must be explicitly false. A nonempty retired media URL array returns 422. A disabled media write gate returns 503 social_media_disabled; invalid ownership, scope, gallery or binding returns 400 invalid_social_media.