feat(caldav): add slot support for feed items

Adds three LLM-fillable slots to every CalDav feed item:
insight, preparation, and crossSource. Slot prompts are
stored in separate .txt files under src/prompts/ with
few-shot examples to steer the LLM away from restating
event details.

Co-authored-by: Ona <no-reply@ona.com>

packages/aris-source-caldav/src/ical-parser.ts

@@ -14,6 +14,13 @@ export interface ICalTimeRange {
 	end: Date
 }
 
+/**
+ * Safety cap to prevent runaway iteration on pathological recurrence rules.
+ * Each iteration is pure date math (no I/O), so a high cap is fine.
+ * 10,000 covers a daily event with DTSTART ~27 years in the past.
+ */
+const MAX_RECURRENCE_ITERATIONS = 10_000
+
 /**
  * Parses a raw iCalendar string and extracts VEVENT components
  * into CalDavEventData objects.
@@ -106,11 +113,23 @@ export function parseICalEvents(
 			continue
 		}
 
-		// Expand recurring event occurrences within the time range
+		// Expand recurring event occurrences within the time range.
+		// The iterator must start from DTSTART (not rangeStart) because
+		// ical.js needs to walk the recurrence rule grid from the original
+		// anchor. We cap iterations to avoid runaway expansion on
+		// pathological rules.
 		const iter = masterEvent.iterator()
 		let next: InstanceType<typeof ICAL.Time> | null = iter.next()
+		let iterations = 0
 
 		while (next) {
+			if (++iterations > MAX_RECURRENCE_ITERATIONS) {
+				console.warn(
+					`[aris.caldav] Recurrence expansion for "${masterEvent.uid}" hit iteration limit (${MAX_RECURRENCE_ITERATIONS}), stopping`,
+				)
+				break
+			}
+
 			// Stop once we're past the range end
 			if (next.compare(rangeEnd) >= 0) break