Implement compact, undo, and init commands

- Add compact command with proper API parameters (providerID, modelID)
- Implement undo command matching TUI behavior:
  - Find previous user message before revert point
  - Restore reverted message to prompt input
  - Filter messages client-side based on session.revert field
- Add init command with proper hex-encoded message ID generation
- Add session.revert field handling:
  - Parse revert field from API responses in fetchSessions and createSession
  - Update revert field via SSE session.updated events
  - Filter messages during render when revert point is set
- Add SSE event handlers for session.compacted and session.error
- Add force reload option to loadMessages for post-compact refresh
- Messages now filter instantly based on revert state without API reload

src/components/message-stream.tsx

@@ -10,6 +10,12 @@ interface MessageStreamProps {
   sessionId: string
   messages: Message[]
   messagesInfo?: Map<string, any>
+  revert?: {
+    messageID: string
+    partID?: string
+    snapshot?: string
+    diff?: string
+  }
   loading?: boolean
 }
 
@@ -57,6 +63,12 @@ export default function MessageStream(props: MessageStreamProps) {
 
     for (const message of props.messages) {
       const messageInfo = props.messagesInfo?.get(message.id)
+
+      // If we hit the revert point, stop rendering messages
+      if (props.revert?.messageID && message.id === props.revert.messageID) {
+        break
+      }
+
       const textParts = message.parts.filter((p) => p.type === "text" && !p.synthetic)
       const toolParts = message.parts.filter((p) => p.type === "tool")
       const reasoningParts = message.parts.filter((p) => p.type === "reasoning")