fix(03): IN-01 document RRULE_PRESETS lossy round-trip v1 limitation

apps/api/src/broker/vevent.ts

@@ -35,6 +35,16 @@ export interface NewEventParams {
 /**
  * Simple RRULE preset strings for whole-series recurring events (D-11 / CAL-07).
  * "weekly on Monday" example: 'FREQ=WEEKLY;BYDAY=MO' (not a key in this map; compose manually).
+ *
+ * IN-01 (v1 limitation — lossy round-trip): these presets map only to a BARE
+ * FREQ=DAILY|WEEKLY|MONTHLY|YEARLY. extractRruleString() preserves the FULL stored RECUR
+ * (which may carry BYDAY/INTERVAL/COUNT/UNTIL), and the preserve-on-edit path keeps that
+ * rich rule. But if a `recurrence` preset value is ever applied to a previously-rich rule,
+ * it COLLAPSES the rule to the bare preset — silently dropping BYDAY/INTERVAL/UNTIL/COUNT.
+ * This is acceptable in v1 only because the picker offers just these four bare presets and
+ * is disabled on edit (EventForm WR-01). When recurrence EDITING ships, do NOT replace the
+ * stored rule with a preset: parse the existing RECUR and modify it in place so qualifiers
+ * survive. See CR-01/WR-01 preserve paths for the precedent.
  */
 export const RRULE_PRESETS: Record<string, string> = {
   daily: 'FREQ=DAILY',