fix(art): keep iTerm2 inline images on screen

iTerm2 images live in the cell grid, unlike Kitty placements: repainting
the mosaic behind them erases the picture. Re-emit the image whenever the
mosaic identity (station + track) changes, even if the artwork bytes are
the same.

Also send doNotMoveCursor=1 to iTerm2 itself so the terminal does not
scroll or jump the cursor out from under Textual's compositor; WezTerm
keeps the previous payload since it is pickier about parameters.

somafm_tui/widgets/art.py

@@ -38,6 +38,29 @@ def _tgp(data: str) -> str:
     return f"\x1b_G{data}\x1b\\"
 
 
+def _iterm2_native() -> bool:
+    """Are we talking to iTerm2 itself (rather than a compatible terminal)?
+
+    WezTerm understands the same OSC 1337 payload but is fussier about
+    parameters it does not know, so the iTerm2-only ones stay gated.
+    """
+    env = os.environ
+    return env.get("LC_TERMINAL", "").lower() == "iterm2" or env.get(
+        "TERM_PROGRAM", ""
+    ).lower() in {"iterm.app", "iterm2"}
+
+
+def _art_key(app) -> str:
+    """Identity of what the mosaic is drawing (station + current track)."""
+    station = app.current
+    if station is None:
+        return ""
+    song = station.now_playing
+    artist = song.artist if song is not None else ""
+    title = song.title if song is not None else ""
+    return f"{station.id}|{artist}|{title}"
+
+
 def _terminal_wrap(sequence: str) -> str:
     """Wrap Kitty sequences for tmux DCS passthrough."""
     term = os.environ.get("TERM", "")
@@ -180,8 +203,8 @@ class ITerm2Image(Widget):
     """Inline image via OSC 1337, injected through Textual's render_lines().
 
     WezTerm and iTerm2 both implement this natively.  ``doNotMoveCursor=1``
-    keeps the terminal cursor sane; the widget then restores it to the
-    bottom-right of the region.
+    (iTerm2 only) keeps the terminal cursor sane; the widget then restores it
+    to the bottom-right of the region.
     """
 
     DEFAULT_CSS = """
@@ -217,8 +240,12 @@ class ITerm2Image(Widget):
         buffer = BytesIO()
         self._image.save(buffer, format="PNG")
         payload = base64.b64encode(buffer.getvalue()).decode("ascii")
+        # ``doNotMoveCursor`` keeps iTerm2 from scrolling/jumping the cursor
+        # out from under Textual's compositor; we place the cursor ourselves.
+        keep_cursor = "doNotMoveCursor=1;" if _iterm2_native() else ""
         data = (
             "\x1b]1337;File=inline=1;"
+            f"{keep_cursor}"
             f"width={width};height={height};"
             f"preserveAspectRatio=0:{payload}\x07"
         )
@@ -280,6 +307,7 @@ class ArtPane(Widget):
         self._image_widget: Widget | None = None
         self._last_data: bytes | None = None
         self._last_size: tuple[int, int] = (0, 0)
+        self._mosaic_key = ""
 
     # ------------------------------------------------------------------ #
     # mosaic background
@@ -292,9 +320,7 @@ class ArtPane(Widget):
             return Text("")
         width = max(1, self.size.width)
         height = max(1, self.size.height)
-        song = station.now_playing
-        key = f"{station.id}|{song.artist if song else ''}|{song.title if song else ''}"
-        return Group(*art_lines(key, width, height))
+        return Group(*art_lines(_art_key(app), width, height))
 
     # ------------------------------------------------------------------ #
     # image overlay
@@ -321,6 +347,14 @@ class ArtPane(Widget):
         width = max(1, self.size.width)
         height = max(1, self.size.height)
 
+        # Repainting the mosaic overwrites the cells an inline (iTerm2) image
+        # occupies, so re-emit the image whenever what is drawn underneath
+        # changes -- even if the artwork bytes happen to be the same.
+        mosaic_key = _art_key(app)
+        if mosaic_key != self._mosaic_key:
+            self._mosaic_key = mosaic_key
+            force = True
+
         if station is not None and data and artwork.supported():
             if (
                 not force