fix(wallet): replace text-marker hack with proper raw event API (room.sendRaw + MsgLikeKind.Other)

- Add Timeline.sendRaw() to send custom Matrix events
- Add CustomEventContent type for receiving custom events
- Update TimelineEventContentMapper to handle MsgLikeKind.Other
- Update TimelineItemContentFactory to intercept payment events
- Rewrite DefaultPaymentEventSender to use sendRaw instead of text markers
- Update TimelineItemContentPaymentFactory to parse raw JSON
- Remove text-marker detection from TimelineItemContentMessageFactory
- Update tests to use raw event API
- Mark raw event SDK blocker as RESOLVED in BLOCKERS.md

Event type: co.sulkta.payment.request (reverse-domain format)
Status updates: co.sulkta.payment.status

Benefits:
- Proper Matrix protocol compliance
- No JSON embedded in text messages
- Events won't be indexed by search
- Clean separation from regular messages

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/RustTimeline.kt

@@ -279,6 +279,15 @@ class RustTimeline(
         }
     }
 
+    override suspend fun sendRaw(
+        eventType: String,
+        content: String,
+    ): Result<Unit> = withContext(dispatcher) {
+        runCatchingExceptions {
+            inner.sendRaw(eventType, content)
+        }
+    }
+
     override suspend fun redactEvent(eventOrTransactionId: EventOrTransactionId, reason: String?): Result<Unit> = withContext(dispatcher) {
         runCatchingExceptions {
             inner.redactEvent(

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/item/event/TimelineEventContentMapper.kt

@@ -29,6 +29,7 @@ import io.element.android.libraries.matrix.api.timeline.item.event.StateContent
 import io.element.android.libraries.matrix.api.timeline.item.event.StickerContent
 import io.element.android.libraries.matrix.api.timeline.item.event.UnableToDecryptContent
 import io.element.android.libraries.matrix.api.timeline.item.event.UnknownContent
+import io.element.android.libraries.matrix.api.timeline.item.event.CustomEventContent
 import io.element.android.libraries.matrix.api.timeline.item.event.UtdCause
 import io.element.android.libraries.matrix.impl.media.map
 import io.element.android.libraries.matrix.impl.poll.map
@@ -111,7 +112,14 @@ class TimelineEventContentMapper(
                             // Live location messages are a special kind of message that we want to treat as unknown content for now
                              UnknownContent
                         }
-                        is MsgLikeKind.Other -> UnknownContent
+                        is MsgLikeKind.Other -> {
+                            // MsgLikeKind.Other contains custom event types
+                            // Pass through the event type so downstream handlers can process it
+                            CustomEventContent(
+                                eventType = kind.eventType,
+                                rawJson = null, // Raw JSON accessed via TimelineItemDebugInfoProvider
+                            )
+                        }
                     }
                 }
                 is TimelineItemContent.ProfileChange -> {