feat: add generic CalDAV calendar data source

Add @aris/source-caldav package that fetches calendar events from any
CalDAV server via tsdav + ical.js.

- Supports Basic auth and OAuth via explicit authMethod discriminant
- serverUrl provided at construction time, not hardcoded
- Optional timeZone for correct local day boundaries
- Credentials cleared from memory after client login
- Failed calendar fetches logged, not silently dropped
- Login promise cached with retry on failure

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

packages/aris-source-caldav/scripts/test-live.ts

@@ -0,0 +1,62 @@
+/**
+ * Live test script for CalDavSource.
+ *
+ * Usage:
+ *   bun run test-live.ts
+ */
+
+import { CalDavSource } from "../src/index.ts"
+
+const serverUrl = prompt("CalDAV server URL:")
+const username = prompt("Username:")
+const password = prompt("Password:")
+const lookAheadRaw = prompt("Look-ahead days (default 0):")
+
+if (!serverUrl || !username || !password) {
+	console.error("Server URL, username, and password are required.")
+	process.exit(1)
+}
+
+const lookAheadDays = Number(lookAheadRaw) || 0
+
+const source = new CalDavSource({
+	serverUrl,
+	authMethod: "basic",
+	username,
+	password,
+	lookAheadDays,
+})
+
+const context = { time: new Date() }
+
+console.log(`\nFetching from ${serverUrl} as ${username} (lookAheadDays=${lookAheadDays})...\n`)
+
+const contextResult = await source.fetchContext(context)
+const items = await source.fetchItems(context)
+
+console.log("=== Context ===")
+console.log(JSON.stringify(contextResult, null, 2))
+
+console.log(`\n=== Feed Items (${items.length}) ===`)
+for (const item of items) {
+	console.log(`\n--- ${item.data.title} ---`)
+	console.log(`  ID:         ${item.id}`)
+	console.log(`  Calendar:   ${item.data.calendarName ?? "(unknown)"}`)
+	console.log(`  Start:      ${item.data.startDate.toISOString()}`)
+	console.log(`  End:        ${item.data.endDate.toISOString()}`)
+	console.log(`  All-day:    ${item.data.isAllDay}`)
+	console.log(`  Location:   ${item.data.location ?? "(none)"}`)
+	console.log(`  Status:     ${item.data.status ?? "(none)"}`)
+	console.log(`  Urgency:    ${item.signals?.urgency}`)
+	console.log(`  Relevance:  ${item.signals?.timeRelevance}`)
+	if (item.data.attendees.length > 0) {
+		console.log(`  Attendees:  ${item.data.attendees.map((a) => a.name ?? a.email).join(", ")}`)
+	}
+	if (item.data.description) {
+		console.log(`  Desc:       ${item.data.description.slice(0, 100)}`)
+	}
+}
+
+if (items.length === 0) {
+	console.log("(no events found in the time window)")
+}