docs(api): document 'obsidian' export format (FR-STORE-4)

docs/04-api-contracts.md

@@ -70,7 +70,10 @@ get_meeting(input: { meetingId: MeetingId }): Meeting          // includes trans
 delete_meeting(input: { meetingId: MeetingId }): void
 // format "bundle" writes a portable folder: audio.wav + transcript.json + notes.md + summary.json
 // (all decrypted) + meeting.json (the MeetingBundle manifest), re-importable on another machine.
-export_meeting(input: { meetingId: MeetingId; dest: string; format: "md" | "pdf" | "docx" | "bundle" }): string
+// format "obsidian" writes one self-contained vault note (dest is a .md file path, no audio):
+// YAML frontmatter (title/date/duration/participants/tags/source) + notes + summary + decisions
+// + action items + timestamped transcript. For dropping a meeting into an Obsidian vault.
+export_meeting(input: { meetingId: MeetingId; dest: string; format: "md" | "pdf" | "docx" | "bundle" | "obsidian" }): string
 // Edit commands that change an uploaded artifact — update_notes, set_tags, generate_summary,
 // reprocess_transcript, confirm_action_items — auto-resync when sync is enabled (FR-SYNC-5):
 // they enqueue for finalize-trigger targets and pump in the background. SHA-256 dedup means an