♻️ refactor(gui): improve left panel readability with better fonts, colors, and layout

- Replace Segoe UI with Roboto for cross-platform compatibility
- Increase font sizes for better readability (9→11, 11→12, 14→15)
- Update dark theme to VS Code-like colors (#1E1E1E bg)
- Brighten accent colors and improve contrast ratios
- Fix StepHeader: number circle background, status icon positioning
- Enlarge accent bar (4→5px) and buttons (28→32px)
- Simplify status text (Completed → Done)
- Improve connector line sizing and alignment

src/gui/main_window.py

@@ -42,6 +42,7 @@ from gui.styles import (
     DANGER_COLOR,
     INFO_COLOR,
     CONNECTOR_COLOR,
+    STEP_ICON_SIZE,
     get_theme,
 )
 from gui.widgets import (
@@ -190,16 +191,17 @@ class MainWindow(ctk.CTk):
             row=0, column=0, sticky="nsew",
             padx=PADDING, pady=PADDING,
         )
-        panel.grid_rowconfigure(9, weight=1)
+        panel.grid_rowconfigure(10, weight=1)
 
+        # ── Title ──
         title = ctk.CTkLabel(
             panel,
             text="Workflow",
             font=FONT_HEADING,
         )
-        title.grid(row=0, column=0, padx=PADDING, pady=PADDING)
+        title.grid(row=0, column=0, padx=PADDING, pady=(PADDING, PADDING_SMALL))
 
-        # Step definitions with descriptions
+        # ── Steps ──
         step_defs = [
             {"num": 1, "title": "Check Environment", "desc": "Verify tools & connectivity"},
             {"num": 2, "title": "Program & Verify Flash", "desc": "Wipe, program, and verify flash"},
@@ -207,7 +209,6 @@ class MainWindow(ctk.CTk):
             {"num": 4, "title": "Load Main Program", "desc": "TFTP upload, reboot, verify boot"},
         ]
 
-        # Create step headers with callbacks
         self._steps = []
         self._step_statuses = {}
         for i, defn in enumerate(step_defs):
@@ -217,24 +218,24 @@ class MainWindow(ctk.CTk):
                 title=defn["title"],
                 description=defn["desc"],
                 callback=lambda idx=i: self._execute_step(idx),
-                can_run=(i == 0),  # First step always runnable
+                can_run=(i == 0),
             )
             self._steps.append(step)
             self._step_statuses[i] = "pending"
 
-            # Add connector line between steps
+            # Connector line between steps
             if i > 0:
                 connector = ctk.CTkFrame(
                     panel,
-                    width=2,
-                    height=8,
+                    width=3,
+                    height=12,
                     fg_color=CONNECTOR_COLOR,
-                    corner_radius=1,
+                    corner_radius=2,
                 )
                 connector.grid(
                     row=i * 2, column=0,
                     sticky="n",
-                    padx=(PADDING_SMALL + 24 + PADDING_SMALL, PADDING_SMALL),
+                    padx=(PADDING_SMALL + STEP_ICON_SIZE + PADDING_SMALL, PADDING_SMALL),
                 )
 
             # Position step
@@ -245,16 +246,16 @@ class MainWindow(ctk.CTk):
                 pady=PADDING_SMALL,
             )
 
-        # Progress indicator
+        # ── Progress indicator ──
         self._progress = ProgressIndicator(panel)
         self._progress.grid(
             row=8, column=0,
             sticky="nsew",
             padx=PADDING,
-            pady=PADDING,
+            pady=(PADDING, PADDING_SMALL),
         )
 
-        # Run button
+        # ── Run All button ──
         self._run_btn = ctk.CTkButton(
             panel,
             text="▶ Run All Steps",
@@ -267,7 +268,7 @@ class MainWindow(ctk.CTk):
             row=9, column=0,
             sticky="nsew",
             padx=PADDING,
-            pady=PADDING,
+            pady=PADDING_SMALL,
         )
 
     def _build_log_panel(self, parent: ctk.CTkFrame) -> None: