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

BLOCKERS.md

@@ -156,55 +156,51 @@
 
 ---
 
-## Task 8: Raw Event Handling ✅ COMPLETE
+## Task 8: Raw Event Handling ✅ COMPLETE (UPGRADED)
+
+### ✅ RESOLVED: SDK Raw Event API
+**Previous blocker:** Matrix Rust SDK did not expose raw event sending or raw JSON access.
+
+**Resolution:** The SDK (version 26.03.24) now provides:
+- `Timeline.sendRaw(eventType: String, content: String)` — Sends custom event types
+- `MsgLikeKind.Other` with `eventType` field — Receives custom events
+- `TimelineItemDebugInfo.originalJson` — Access to raw event JSON via debug info provider
+
+**Implementation updated to use proper raw events instead of text markers.**
 
 ### Completed
 - ✅ **PaymentEventSender.kt** — Interface for sending payment events
-- ✅ **DefaultPaymentEventSender.kt** — Implementation
-  - Sends payment as formatted text message with JSON payload
-  - Format: `[cardano-payment:v1]{...json...}\n💰 Sent X ADA`
-  - HTML body includes data-payment attribute for future parsing
-  - Status updates use separate marker: `[cardano-payment-status:v1]`
-- ✅ **TimelineItemContentPaymentFactory.kt** — Parser for payment messages
-  - `isPaymentEvent(body)` — Detects payment marker
-  - `isPaymentStatusUpdate(body)` — Detects status update marker
-  - `createFromBody(body, isSentByMe)` — Parses text message body
-  - `createFromRaw(json, isSentByMe)` — Parses raw JSON (for future SDK extension)
+- ✅ **DefaultPaymentEventSender.kt** — Implementation using raw events
+  - Uses `timeline.sendRaw(eventType, content)` to send custom events
+  - Event type: `co.sulkta.payment.request` (reverse-domain format)
+  - Status updates: `co.sulkta.payment.status`
+  - No text marker hack — proper Matrix custom events
+- ✅ **TimelineItemContentPaymentFactory.kt** — Parser for payment events
+  - `isPaymentEventType(eventType)` — Checks for payment event type
+  - `isStatusUpdateEventType(eventType)` — Checks for status update type
+  - `createFromRaw(json, isSentByMe)` — Parses raw JSON from custom events
+  - Supports both camelCase and snake_case field names
   - Graceful error handling — returns null on malformed JSON
-- ✅ **TimelineItemContentMessageFactory.kt** — Modified to intercept payments
-  - Added paymentFactory dependency
-  - Added isSentByMe parameter to create()
-  - TextMessageType checks for payment marker before creating text content
-- ✅ **TimelineItemContentFactory.kt** — Passes isSentByMe to message factory
+- ✅ **TimelineEventContentMapper.kt** — Maps `MsgLikeKind.Other` to `CustomEventContent`
+- ✅ **TimelineItemContentFactory.kt** — Handles `CustomEventContent` for payments
+  - Gets raw JSON via `timelineItemDebugInfoProvider().originalJson`
+  - Delegates to paymentFactory for payment event types
+- ✅ **CustomEventContent.kt** — New EventContent type for custom events
+- ✅ **Timeline.sendRaw()** — Added to Timeline interface and RustTimeline implementation
 - ✅ **FakePaymentEventSender.kt** — Test fake
-- ✅ **TimelineItemContentPaymentFactoryTest.kt** — Unit tests
-
-### SDK Limitations & Approach
-The Matrix Rust SDK does NOT expose:
-- Raw event sending (`room.sendRawEvent()`)
-- Raw JSON access for UnknownContent
-
-**Workaround implemented:**
-Instead of custom event types, we encode payment data in standard text messages:
-```
-[cardano-payment:v1]{"amount_lovelace":10000000,"to_address":"...","from_address":"...","tx_hash":"...","status":"pending","network":"testnet"}
-💰 Sent 10 ADA
-```
-
-This approach:
-- Works with existing SDK (no fork needed)
-- Falls back gracefully (non-wallet clients see "💰 Sent 10 ADA")
-- Can be upgraded to proper custom events when SDK exposes raw event APIs
+- ✅ **TimelineItemContentPaymentFactoryTest.kt** — Updated unit tests
 
 ### m.replace Status Updates
-**Decision:** Due to SDK limitations (no direct access to m.replace relations), status updates are sent as new messages rather than event replacements.
+**Decision:** Status updates are sent as separate events of type `co.sulkta.payment.status`.
 
 **Future improvement:** When SDK exposes event relations, refactor to use m.replace for cleaner status update thread.
 
-### Potential Issues
-- ⚠️ Status updates create new timeline events (not ideal, but works)
-- ⚠️ Payment messages may be indexed by search (contains JSON)
-- ⚠️ Very long addresses in JSON may hit message length limits (unlikely in practice)
+### Benefits of Raw Event Approach
+- ✅ Proper Matrix protocol compliance (custom event types, not hacked text)
+- ✅ Non-wallet clients see "Unknown event" instead of JSON-in-text
+- ✅ Clean separation of payment events from regular messages
+- ✅ Events won't be indexed by message search
+- ✅ No message length limits concern
 
 ---