feat(location): send MSC3488-compliant shared-location events

Location sharing sent only a legacy geo_uri with a "Location: geo:..." body, so
other clients often rendered it as plain text. Include the MSC3488 blocks
(org.matrix.msc3488.location/asset/ts + m.ts) alongside geo_uri and a readable
body, so Element and others render a proper location pin. Local rendering is
unchanged (still reads geo_uri).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/RoomInput.tsx

@@ -251,10 +251,18 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
           setLocating(false);
           const { latitude, longitude } = pos.coords;
           const geoUri = `geo:${latitude.toFixed(6)},${longitude.toFixed(6)}`;
+          const ts = Date.now();
+          // MSC3488 extensible location: send the geo_uri (legacy) alongside the
+          // m.location/m.asset/m.ts blocks so Element and other clients render a
+          // proper "shared location" pin instead of falling back to plain text.
           mx.sendMessage(roomId, threadRootId ?? null, {
             msgtype: 'm.location',
-            body: `Location: ${geoUri}`,
+            body: `Shared a location: ${geoUri}`,
             geo_uri: geoUri,
+            'org.matrix.msc3488.location': { uri: geoUri },
+            'org.matrix.msc3488.asset': { type: 'm.self' },
+            'org.matrix.msc3488.ts': ts,
+            'm.ts': ts,
           } as any);
         },
         (err) => {