fix: CLI poll loop used UUID instead of queue cursor (last_id)

The poll loop was storing msg.ID (UUID string) as afterID, but the server
expects the integer queue cursor from last_id. This caused the CLI to
re-fetch ALL messages on every poll cycle.

- Change PollMessages to accept int64 afterID and return PollResult with LastID
- Track lastQID (queue cursor) instead of lastMsgID (UUID)
- Parse the wrapped MessagesResponse properly

cmd/chat-cli/api/client.go

@@ -97,21 +97,18 @@ func (c *Client) SendMessage(msg *Message) error {
 	return err
 }
 
-// PollMessages long-polls for new messages.
-func (c *Client) PollMessages(afterID string, timeout int) ([]Message, error) {
+// PollMessages long-polls for new messages. afterID is the queue cursor (last_id).
+func (c *Client) PollMessages(afterID int64, timeout int) (*PollResult, error) {
 	// Use a longer HTTP timeout than the server long-poll timeout.
 	client := &http.Client{Timeout: time.Duration(timeout+5) * time.Second}
 
 	params := url.Values{}
-	if afterID != "" {
-		params.Set("after", afterID)
+	if afterID > 0 {
+		params.Set("after", fmt.Sprintf("%d", afterID))
 	}
 	params.Set("timeout", fmt.Sprintf("%d", timeout))
 
-	path := "/api/v1/messages"
-	if len(params) > 0 {
-		path += "?" + params.Encode()
-	}
+	path := "/api/v1/messages?" + params.Encode()
 
 	req, err := http.NewRequest("GET", c.BaseURL+path, nil)
 	if err != nil {
@@ -134,18 +131,15 @@ func (c *Client) PollMessages(afterID string, timeout int) ([]Message, error) {
 		return nil, fmt.Errorf("HTTP %d: %s", resp.StatusCode, string(data))
 	}
 
-	// The server may return an array directly or wrapped.
-	var msgs []Message
-	if err := json.Unmarshal(data, &msgs); err != nil {
-		// Try wrapped format.
-		var wrapped MessagesResponse
-		if err2 := json.Unmarshal(data, &wrapped); err2 != nil {
-			return nil, fmt.Errorf("decode messages: %w (raw: %s)", err, string(data))
-		}
-		msgs = wrapped.Messages
+	var wrapped MessagesResponse
+	if err := json.Unmarshal(data, &wrapped); err != nil {
+		return nil, fmt.Errorf("decode messages: %w (raw: %s)", err, string(data))
 	}
 
-	return msgs, nil
+	return &PollResult{
+		Messages: wrapped.Messages,
+		LastID:   wrapped.LastID,
+	}, nil
 }
 
 // JoinChannel joins a channel via the unified command endpoint.