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>

android/app/src/main/java/com/fabledsword/inkwell/ui/EditorAction.kt

@@ -80,10 +80,9 @@ sealed interface EditorAction {
     /**
      * Mark the reminder dealt with.
      *
-     * Distinct from [ClearReminder] even though the core does the same thing to
-     * the column today: this is where recurrence advancement lands when it is
-     * built, so a recurring reminder finished through the generic clear would
-     * silently stop recurring.
+     * Distinct from [ClearReminder]: a recurring reminder moves on to its next
+     * occurrence here, and only a one-off is cleared, so a recurring reminder
+     * finished through the generic clear would stop recurring.
      */
     data object CompleteReminder : EditorAction