fix: show notifications and unread count for SSE messages arriving when chat closed

Three gaps caused messages received via SSE to be invisible when
the conversation buffer wasn't already open:

1. Echo-area notification (noise-receive.el): when an SSE message
   arrives and the conversation buffer isn't in a visible window,
   show "[Noise] <name>" in the echo area.

2. Modeline unread counter (noise.el): the noise-mode lighter now
   shows Noise[N] for N unread messages via a lightweight SUM
   aggregation across all conversations.

3. Auto-refresh hook (noise-conversation.el): a
   window-buffer-change-functions hook re-renders *signal:* buffers
   when they become visible, covering direct C-x b switches.

Also adds regression test:
noise-receive-sse-stores-then-open-shows-message —
store via SSE handler with no buffer open, then open and verify.

noise-conversation.el

@@ -245,5 +245,19 @@ NAME is the contact typing; ACTION is signal-cli's STARTED or STOPPED."
     (with-current-buffer buf
       (noise-chat-list--render))))
 
+;;; Auto-refresh when conversation buffers become visible
+
+(defun noise-conversation--on-buffer-visible (_frame)
+  "Refresh any stale `*signal:*' conversation buffer that just became visible."
+  (dolist (window (window-list nil 'never (selected-frame)))
+    (when-let ((buf (window-buffer window)))
+      (when (and (string-prefix-p "*signal:" (buffer-name buf))
+                 (not (string= "*signal*" (buffer-name buf))))
+        (with-current-buffer buf
+          (when (derived-mode-p 'noise-conversation-mode)
+            (noise-conversation--render)))))))
+
+(add-hook 'window-buffer-change-functions #'noise-conversation--on-buffer-visible)
+
 (provide 'noise-conversation)
 ;;; noise-conversation.el ends here

noise-receive.el

@@ -44,13 +44,22 @@ Returns the number of new messages stored."
       (message "Received %d new message%s" new (if (= new 1) "" "s")))
     new))
 
+(defun noise-receive--announce-message (conv-id)
+  "Show a brief echo-area notification for a new message in CONV-ID."
+  (let* ((conv (noise-db-get-conversation conv-id))
+         (name (if conv (or (gethash "name" conv) conv-id) conv-id)))
+    (message "[Noise] %s" name)))
+
 (defun noise-receive--handle-sse-event (event)
   "Handle an SSE EVENT from signal-cli.
 Processes the envelope and updates UI."
   (noise-db-init)
   (when-let ((envelope (noise-receive--field event "envelope")))
     (when-let ((conv-id (noise-receive--process-envelope envelope)))
-      (noise-conversation-refresh-for conv-id)
+      (let ((buf (noise-conversation--buffer-for conv-id)))
+        (if (and buf (get-buffer-window buf t))
+            (noise-conversation-refresh-for conv-id)
+          (noise-receive--announce-message conv-id)))
       (when-let ((buf (get-buffer "*signal*")))
         (with-current-buffer buf
           (noise-chat-list--render))))))

noise.el

@@ -76,11 +76,27 @@ Queries the daemon for registered accounts and sets `noise-account'."
     (noise-rpc-error
      (message "Error: %s" (cdr err)))))
 
+(defun noise--unread-lighter ()
+  "Return the mode-line lighter string with unread count."
+  (let ((count 0))
+    (when (and (boundp 'noise-db--connection)
+               noise-db--connection
+               (fboundp 'sqlitep)
+               (sqlitep noise-db--connection))
+      (condition-case nil
+          (setq count (or (caar (sqlite-select noise-db--connection
+                                                "SELECT COALESCE(SUM(unread_count), 0) FROM conversations"))
+                          0))
+        (error 0)))
+    (if (> count 0)
+        (format " Noise[%d]" count)
+      " Noise")))
+
 ;;;###autoload
 (define-minor-mode noise-mode
   "Toggle Noise Signal client mode."
   :global t
-  :lighter " Noise"
+  :lighter (:eval (noise--unread-lighter))
   :group 'noise
   (if noise-mode
       (progn
@@ -88,6 +104,5 @@ Queries the daemon for registered accounts and sets `noise-account'."
         (noise-receive-start-sse))
     (noise-receive-stop-sse)
     (message "Noise mode disabled")))
-
 (provide 'noise)
 ;;; noise.el ends here

test/noise-receive-test.el

@@ -208,3 +208,28 @@
      (should (string-match-p "Sarah> from sse" (buffer-string))))
    (let ((msg (car (noise-db-get-messages "+1"))))
      (should (string= "from sse" (gethash "body" msg))))))
+
+(ert-deftest noise-receive-sse-stores-then-open-shows-message ()
+  "An SSE event stores the message; opening the conversation later shows it."
+  (noise-receive-test--with-db
+   ;; No conversation buffer open — simulate SSE event arriving
+   (noise-receive--handle-sse-event
+    (noise-receive-test--ht
+     "envelope"
+     (noise-receive-test--ht
+      "sourceNumber" "+1" "sourceName" "Sarah"
+      "dataMessage" (noise-receive-test--ht
+                     "timestamp" 1717930000000
+                     "message" "hello from the void"))))
+   ;; Verify message is in DB
+   (let ((msgs (noise-db-get-messages "+1")))
+     (should (= 1 (length msgs)))
+     (should (string= "hello from the void" (gethash "body" (car msgs)))))
+   ;; Verify conversation has unread count
+   (let ((conv (noise-db-get-conversation "+1")))
+     (should (= 1 (gethash "unread_count" conv))))
+   ;; Now open the conversation and verify message renders
+   (require 'noise-conversation)
+   (with-current-buffer (noise-conversation-open "+1")
+     (should (string-match-p "Sarah> hello from the void" (buffer-string)))
+     (should (= 0 (gethash "unread_count" (noise-db-get-conversation "+1")))))))