🐛 fix(gui): single-step execution now runs only selected step

- Add single_step parameter to _run_steps_worker
- _execute_step now passes single_step=True
- _run_all_steps passes single_step=False explicitly
- Single step execution no longer runs subsequent steps

src/gui/main_window.py

@@ -780,18 +780,17 @@ class MainWindow(ctk.CTk):
         self._run_btn.configure(state="disabled", text="Running...")
         self._progress.reset()
 
-        # Reset status for this step and all after it
-        for i in range(index, len(self._steps)):
-            self._step_statuses[i] = "pending"
-            self._steps[i].set_status("pending")
+        # Reset status for this step only
+        self._step_statuses[index] = "pending"
+        self._steps[index].set_status("pending")
 
         self._progress.set_value(0.0)
 
-        # Start background worker thread
+        # Start background worker thread with single_step=True
         self._worker_thread = threading.Thread(
             target=self._run_steps_worker,
             daemon=True,
-            args=(index,),
+            args=(index, True),  # single_step=True
         )
         self._worker_thread.start()
 
@@ -823,15 +822,16 @@ class MainWindow(ctk.CTk):
         self._worker_thread = threading.Thread(
             target=self._run_steps_worker,
             daemon=True,
-            args=(0,),  # Start from step 0
+            args=(0, False),  # single_step=False
         )
         self._worker_thread.start()
 
-    def _run_steps_worker(self, start_index: int = 0) -> None:
+    def _run_steps_worker(self, start_index: int = 0, single_step: bool = False) -> None:
         """Worker method that runs workflow steps in the background.
 
         Args:
             start_index: Index of the first step to run (0-based).
+            single_step: If True, only run the step at start_index.
         """
         step_funcs = [
             self._run_step_1_check_environment,
@@ -840,10 +840,12 @@ class MainWindow(ctk.CTk):
             self._run_step_4_load_main_program,
         ]
 
-        total = len(step_funcs) - start_index
+        # Determine end index based on single_step flag
+        end_index = start_index + 1 if single_step else len(step_funcs)
+        total = end_index - start_index
         results: list[bool] = []
 
-        for i in range(start_index, len(step_funcs)):
+        for i in range(start_index, end_index):
             step_idx = i - start_index
             self._set_step_status(i, "running")
             self._progress.set_value(step_idx / total)
@@ -860,7 +862,7 @@ class MainWindow(ctk.CTk):
             self._progress.set_value((step_idx + 1) / total)
 
             # Stop on first failure when running all steps
-            if start_index == 0 and not success:
+            if not single_step and not success:
                 break
 
             # Inter-step delay (skip after last step)