M7: polish + E2E + docs (layout pass, theming, states, e2e driver, schema, setup.md, security)

docs/04-wire-protocol.md

@@ -183,10 +183,21 @@ Agent-sent media is available; app pulls bytes.
    "media_id":"md_5","kind":"video","mime":"video/mp4","size":123456,"filename":"clip.mp4"}}
 ```
 
-### `status`
-Gateway lifecycle / session info.
+### `read.receipt`
+The gateway acknowledges that the agent has received and started processing
+the user's message. The app uses it to show ✓✓ on user bubbles.
 ```json
-{"type":"status","payload":{"state":"online","session":{"chat_id":"…","model":"…","tokens":11}}}
+{"type":"read.receipt","chat_id":"android:default","payload":{"message_id":"m_9001"}}
+```
+Emitted to the originating connection when a `message.send` is accepted for
+processing (at the moment it is handed to the agent), for user-originated
+messages only.
+
+### `status`
+Gateway health state. Broadcast to all connected clients at startup
+(`state: "online"`); `restarting` / `degraded` are reserved for future use.
+```json
+{"type":"status","payload":{"state":"online"}}
 ```
 `state` ∈ `online | restarting | degraded`.