DRY pass #2, batch 8: the Rust and ffi docs (#5372)

sync/mod.rs listed 5 of its 9 modules; migrate's doc sat above the v9 SQL;
client.rs had items after its test module; the ffi's sync_now doc had fused
into client_update's; complete_reminder (ffi and EditorAction) still said
recurrence advancement was to come, though the core does it; NoteQuery.view
listed views the core never matched and claimed it validated. Test scratch
dirs drop the old ts-/iw- prefixes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

core/src/sync/mod.rs

@@ -8,6 +8,10 @@
 //! - `client` — HTTP transport: the handshake call and device-token auth.
 //! - `state` — the persisted link record (server, token, change-feed cursor).
 //! - `engine` — one full cycle: push local changes, then pull the server's.
+//! - `link` — linking a device to a server and unlinking it, one flow for every client.
+//! - `pull` / `push` — the two halves of that cycle.
+//! - `wire` — the delta-feed JSON shapes, as the server sends them.
+//! - `blobs` — attachment bytes on disk, filed under their own sha256.
 //! - `sharing` — the Share dialog's calls, straight to the server (#5175).
 //!
 //! The UI surface that drives this lives in whichever client is wrapping the crate,