fix(cli): prepend queued notes safely to multimodal messages

Sending an image to a vision model turns the user message into a list of
OpenAI-style content parts. When a /model or /reload-skills note was queued
for the same turn, the CLI did `note + "\n\n" + agent_message`, crashing the
agent thread with:

    TypeError: can only concatenate str (not "list") to str

Repro: `/model gpt-5.5 --provider openai-codex`, then paste+send an image.

Add _prepend_note_to_message(), which folds the note into the first text
part of a content-parts list (or inserts a leading text part for image-only
messages) and keeps the plain-string path unchanged. Used for both the
model-switch and skills-reload notes.

cli.py

@@ -2116,6 +2116,39 @@ def _cprint(text: str):
             pass
 
 
+def _prepend_note_to_message(message, note: str):
+    """Prepend a one-shot system-style note to a user message.
+
+    ``message`` is normally a plain string, but when the user attaches an image
+    to a vision-capable model it becomes a list of OpenAI-style content parts
+    (text + ``image_url`` blocks). Naively doing ``note + "\\n\\n" + message``
+    then raises ``TypeError: can only concatenate str (not "list") to str`` —
+    e.g. running ``/model ...`` (which queues a model-switch note) and then
+    sending a pasted image in the same turn.
+
+    Returns the message with ``note`` prepended:
+      * ``str``  → ``f"{note}\\n\\n{message}"``
+      * ``list`` → note folded into the first text part, or inserted as a new
+        leading ``{"type": "text"}`` part when there is no text part.
+    Unknown shapes are returned unchanged (fail-open).
+    """
+    if not note:
+        return message
+    if isinstance(message, str):
+        return f"{note}\n\n{message}"
+    if isinstance(message, list):
+        parts = list(message)
+        for i, part in enumerate(parts):
+            if isinstance(part, dict) and part.get("type") == "text":
+                merged = dict(part)
+                merged["text"] = f"{note}\n\n{part.get('text', '')}"
+                parts[i] = merged
+                return parts
+        # No text part (image-only) — insert the note as a leading text block.
+        return [{"type": "text", "text": note}, *parts]
+    return message
+
+
 # ---------------------------------------------------------------------------
 # File-drop / local attachment detection — extracted as pure helpers for tests.
 # ---------------------------------------------------------------------------
@@ -12135,17 +12168,21 @@ class HermesCLI:
                     reset_current_session_key = None  # type: ignore[assignment]
                     _approval_session_token = None
                 agent_message = _voice_prefix + message if _voice_prefix else message
-                # Prepend pending model switch note so the model knows about the switch
+                # Prepend pending notes via _prepend_note_to_message, which
+                # handles both plain-string and multimodal content-parts list
+                # messages. Naive ``note + "\n\n" + agent_message`` crashed with
+                # TypeError when an image was attached (agent_message is a list)
+                # and a /model or /reload-skills note was queued for the turn.
                 _msn = getattr(self, '_pending_model_switch_note', None)
                 if _msn:
-                    agent_message = _msn + "\n\n" + agent_message
+                    agent_message = _prepend_note_to_message(agent_message, _msn)
                     self._pending_model_switch_note = None
                 # Prepend pending /reload-skills note so the model sees which
                 # skills were added/removed before handling this turn. Same
                 # one-shot queue pattern as the model-switch note above.
                 _srn = getattr(self, '_pending_skills_reload_note', None)
                 if _srn:
-                    agent_message = _srn + "\n\n" + agent_message
+                    agent_message = _prepend_note_to_message(agent_message, _srn)
                     self._pending_skills_reload_note = None
                 try:
                     result = self.agent.run_conversation(