fix(gui): keep the file-name preview in the plain theme color

Dawn: the red "file exists" tint on the path label reads as an error
across the whole panel. The Run guard's popup already reports a clash,
so the label stays in the standard text color. The popup now also asks
the user to run the data collection again after the run number bump.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/aare/gui/panels/file_path_panel.py

@@ -7,7 +7,6 @@ from aarecommon.models.models import DAQStatusModel, SampleShortInfo
 from PySide6.QtCore import Qt, Signal, Slot
 from PySide6.QtWidgets import QGridLayout, QLabel, QLineEdit, QMessageBox, QSpinBox, QWidget
 
-from aare.gui.styles import PATH_WARN_TEXT
 from aare.gui.widgets.title_label import TitleLabel
 
 ## Logic for filenames:
@@ -165,13 +164,11 @@ class FilePathPanel(QWidget):
         # Store the GUI’s base (without applying scan-kind transforms) for wiring into requests later
         self._filename = self._expand_macros(base, run_number)
 
-        # Preview label shows the effective path (what will be written)
+        # Preview label shows the effective path (what will be written), in the
+        # plain theme color: a clash is reported by the Run guard's popup, not
+        # by a red label.
         effective = self._effective_dataset_base(self._filename)
-        exists = self._exists_for_run(self._filename)
         self.file_name_label.setText(effective + "_master.h5")
-        # Empty stylesheet = reset to the THEME text color (a hardcoded
-        # "default" black would be invisible on the dark theme).
-        self.file_name_label.setStyleSheet(f"color: {PATH_WARN_TEXT};" if exists else "")
         self.path_updated.emit(self._filename)
 
     @Slot()
@@ -257,6 +254,6 @@ class FilePathPanel(QWidget):
             self,
             "File exists",
             f"File already exists:\n{path}\n\n"
-            f"Run number increased to {self.run_number_edit.value()}.",
+            f"Run number increased to {self.run_number_edit.value()}. Please run data collection again.",
         )
         return False

tests/unit/gui/test_data_collection_settings.py

@@ -518,11 +518,9 @@ def test_run_is_blocked_with_a_popup_when_the_file_exists(file_panel, monkeypatc
     boxes = []
     monkeypatch.setattr(QMessageBox, "warning", lambda *a, **k: boxes.append(a))
 
-    # Editing never skips a taken run silently: the name stays literal and
-    # the label only turns red.
+    # Editing never skips a taken run silently: the name stays literal.
     file_panel.set_scan_kind("rotation")
     assert file_panel.run_number_edit.value() == 1
-    assert file_panel.file_name_label.styleSheet() != ""
 
     assert file_panel.file_path_error_box(scan_kind="rotation") is False
     assert len(boxes) == 1
@@ -555,11 +553,10 @@ def test_a_derived_dataset_counts_as_taken(file_panel, monkeypatch):
 
 
 def test_a_directory_or_a_sibling_run_is_not_taken(file_panel, monkeypatch):
-    # Only the exact master files count; anything else would paint runs red
-    # that nothing will write.
+    # Only the exact master files count; anything else would block runs that
+    # nothing will write.
     _taken(monkeypatch, "raster/d/x_001", "raster/d/x_0011_master.h5", "raster/d/x_001_data.h5")
     file_panel.set_scan_kind("raster")
-    assert file_panel.file_name_label.styleSheet() == ""
     assert file_panel.file_path_error_box(scan_kind="raster") is True