feat(audio-rooms): "Listen to recording" CTA for closed rooms

Wire MeetingSpaceEvent's existing RecordingTag into the
note-view renderer. Closed rooms (status=CLOSED) that ship a
`["recording", url]` tag get an OutlinedButton that hands the
URL to the system media player via ACTION_VIEW — most users have
a podcast / audio app registered for HTTPS audio URLs.

Live and scheduled rooms keep the Join button. Closed rooms
without a recording render no CTA — there's nothing to enter.

Adds:
  * MeetingSpaceEvent.recording() accessor
  * TagArrayBuilder<MeetingSpaceEvent>.recording(url) DSL builder
  * ListenToRecordingButton composable in the note renderer

Note: nostrnests' moq-lite refactor dropped the LiveKit-era
recording HTTP surface, but the kind-30312 `recording` tag is
still spec-allowed and individual hosts can populate it via
out-of-band capture. This commit makes Amethyst the receiving
end for any host who does.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/MeetingSpace.kt

@@ -101,6 +101,7 @@ fun RenderMeetingSpaceEventInner(
     val summary = remember(eventUpdates) { noteEvent.summary() }
     val status = remember(eventUpdates) { noteEvent.status() }
     val starts = remember(eventUpdates) { noteEvent.starts() }
+    val recording = remember(eventUpdates) { noteEvent.recording() }
     val participants = remember(eventUpdates) { noteEvent.participants() }
 
     Row(
@@ -160,17 +161,20 @@ fun RenderMeetingSpaceEventInner(
 
     RenderParticipants(participants, accountViewModel, nav)
 
-    // In-feed Join button — closes the deep-link loop. A
-    // `nostr:naddr1...` for a kind-30312 lands here through
-    // MainActivity's URI handler → Route.Note(addressTag) → this
-    // renderer; without a button the user has no path into the
-    // audio room. JoinAudioRoomButton hides itself when the
-    // event lacks service / endpoint / d-tag.
-    if (status != MeetingSpaceStatusTag.STATUS.CLOSED) {
+    // In-feed CTA. Live / scheduled rooms get a Join button; closed
+    // rooms with a recording get a "Listen to recording" button so
+    // audience members who missed the live session can listen back.
+    // Closed rooms without a recording stay button-less — there's
+    // nothing to enter.
     Row(
         modifier = Modifier.fillMaxWidth().padding(top = 8.dp),
         horizontalArrangement = Arrangement.End,
     ) {
+        if (status == MeetingSpaceStatusTag.STATUS.CLOSED) {
+            recording?.let {
+                ListenToRecordingButton(url = it)
+            }
+        } else {
             com.vitorpamplona.amethyst.ui.screen.loggedIn.audiorooms.room.JoinAudioRoomButton(
                 event = noteEvent,
                 accountViewModel = accountViewModel,
@@ -179,6 +183,29 @@ fun RenderMeetingSpaceEventInner(
     }
 }
 
+/**
+ * Hand off a kind-30312 `recording` URL to the system media
+ * player via ACTION_VIEW. Most users have a podcast / audio app
+ * registered for `https://...mp3`-style URLs; the system picker
+ * lets them choose. Stays out of the in-app audio path on
+ * purpose — Amethyst doesn't ship its own audio player surface.
+ */
+@Composable
+private fun ListenToRecordingButton(url: String) {
+    val context = androidx.compose.ui.platform.LocalContext.current
+    androidx.compose.material3.OutlinedButton(onClick = {
+        runCatching {
+            context.startActivity(
+                android.content
+                    .Intent(android.content.Intent.ACTION_VIEW, android.net.Uri.parse(url))
+                    .addFlags(android.content.Intent.FLAG_ACTIVITY_NEW_TASK),
+            )
+        }
+    }) {
+        Text(stringRes(R.string.audio_room_listen_to_recording))
+    }
+}
+
 @Composable
 fun RenderMeetingRoomEvent(
     baseNote: Note,

amethyst/src/main/res/values/strings.xml

@@ -503,6 +503,7 @@
     <string name="audio_room_connecting_handshake">Negotiating audio</string>
     <string name="audio_room_connected">Audio connected</string>
     <string name="audio_room_reconnecting">Reconnecting…</string>
+    <string name="audio_room_listen_to_recording">Listen to recording</string>
     <string name="audio_room_audio_failed">Audio failed: %1$s</string>
     <string name="audio_room_audio_unavailable">Audio is not available for this room</string>
     <string name="audio_room_talk">Talk</string>

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip53LiveActivities/meetingSpaces/MeetingSpaceEvent.kt

@@ -93,6 +93,15 @@ class MeetingSpaceEvent(
      */
     fun font() = tags.firstNotNullOfOrNull(com.vitorpamplona.quartz.nip53LiveActivities.meetingSpaces.tags.FontTag::parse)
 
+    /**
+     * Optional URL to a post-room recording. Hosts that record a
+     * room re-publish the kind-30312 with `status=closed` and
+     * `["recording", url]` so audience members who missed the live
+     * session can listen back. Returns null when no recording is
+     * available.
+     */
+    fun recording() = tags.firstNotNullOfOrNull(com.vitorpamplona.quartz.nip53LiveActivities.meetingSpaces.tags.RecordingTag::parse)
+
     /**
      * Scheduled start time as unix seconds, only meaningful when
      * [status] is [StatusTag.STATUS.PLANNED]. Returns null on

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip53LiveActivities/meetingSpaces/TagArrayBuilderExt.kt

@@ -61,6 +61,12 @@ fun TagArrayBuilder<MeetingSpaceEvent>.font(
         .assemble(family, url),
 )
 
+fun TagArrayBuilder<MeetingSpaceEvent>.recording(url: String) =
+    addUnique(
+        com.vitorpamplona.quartz.nip53LiveActivities.meetingSpaces.tags.RecordingTag
+            .assemble(url),
+    )
+
 fun TagArrayBuilder<MeetingSpaceEvent>.relays(urls: List<NormalizedRelayUrl>) = addUnique(RelayListTag.assemble(urls))
 
 fun TagArrayBuilder<MeetingSpaceEvent>.participant(