Use themed preview accents

Apply the theme-specific accent colour to exclusion previews so new shapes match the final outline in both light and dark modes.

app/gui/exclusions.py

@@ -20,12 +20,13 @@ class ExclusionMixin:
                     self.canvas_orig.delete(preview_id)
                 except Exception:
                     pass
+            accent = self._exclusion_preview_colour()
             self._stroke_preview_id = self.canvas_orig.create_line(
                 x,
                 y,
                 x,
                 y,
-                fill="yellow",
+                fill=accent,
                 width=2,
                 smooth=True,
                 capstyle="round",
@@ -39,7 +40,8 @@ class ExclusionMixin:
                 self.canvas_orig.delete(self._rubber_id)
             except Exception:
                 pass
-        self._rubber_id = self.canvas_orig.create_rectangle(x, y, x, y, outline="yellow", width=2)
+        accent = self._exclusion_preview_colour()
+        self._rubber_id = self.canvas_orig.create_rectangle(x, y, x, y, outline=accent, width=2)
 
     def _exclude_drag(self, event):
         mode = getattr(self, "exclude_mode", "rect")
@@ -153,6 +155,7 @@ class ExclusionMixin:
         next_mode = "free" if current == "rect" else "rect"
         self.exclude_mode = next_mode
         self._current_stroke = None
+        accent = self._exclusion_preview_colour()
         if next_mode == "free":
             if self._rubber_id:
                 try:
@@ -168,6 +171,7 @@ class ExclusionMixin:
                 except Exception:
                     pass
                 self._stroke_preview_id = None
+            self._rubber_id = None
         message_key = "status.free_draw_enabled" if next_mode == "free" else "status.free_draw_disabled"
         if hasattr(self, "status"):
             try:
@@ -186,6 +190,10 @@ class ExclusionMixin:
                 compressed.append(point)
         return compressed
 
+    def _exclusion_preview_colour(self) -> str:
+        is_dark = getattr(self, "theme", "light") == "dark"
+        return "#ffd700" if is_dark else "#c56217"
+
     @staticmethod
     def _close_polygon(points: list[tuple[int, int]]) -> list[tuple[int, int]]:
         """Ensure the polygon is closed by repeating the start if necessary."""