Improve --diff report output with columnar format

Enhanced readability with table-style columnar output

Changes:
- Converted vertical list format to columnar table format
- First column: Parameter name
- Second column: Device 1 value
- Third column: Device 2 value
- Added header row with device names
- Auto-adjusts column widths based on content
- Truncates very long values (>60 chars) with "..."
- Maintains section separation (Firmware, Network, MQTT, etc.)

Before:
  SetOption32:
    KitchenMain = 40
    KitchenBar  = 8

After:
  Parameter        KitchenMain-3040      KitchenBar-7845
  ---------------  --------------------  --------------------
  SetOption32      40                    8

Much easier to scan and compare values side-by-side!

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

device_diff.py

@@ -240,18 +240,44 @@ class DeviceComparison:
 
     def _print_differences(self, differences: List[Dict], device1_name: str, device2_name: str) -> None:
         """
-        Print list of differences in readable format.
+        Print list of differences in columnar format.
 
         Args:
             differences: List of difference dictionaries
             device1_name: First device name
             device2_name: Second device name
         """
-        for diff in differences:
-            key = diff['key']
-            val1 = diff['device1_value']
-            val2 = diff['device2_value']
+        if not differences:
+            return
 
-            print(f"\n{key}:")
-            print(f"  {device1_name:20} = {val1}")
-            print(f"  {device2_name:20} = {val2}")
+        # Calculate column widths
+        max_key_len = max(len(str(diff['key'])) for diff in differences)
+        max_val1_len = max(len(str(diff['device1_value'])) for diff in differences)
+        max_val2_len = max(len(str(diff['device2_value'])) for diff in differences)
+
+        # Ensure minimum column widths
+        key_width = max(max_key_len, 15)
+        val1_width = max(max_val1_len, len(device1_name), 20)
+        val2_width = max(max_val2_len, len(device2_name), 20)
+
+        # Truncate device names if too long for column headers
+        dev1_header = device1_name[:val1_width]
+        dev2_header = device2_name[:val2_width]
+
+        # Print header row
+        print(f"\n{'Parameter':<{key_width}}  {dev1_header:<{val1_width}}  {dev2_header:<{val2_width}}")
+        print("-" * key_width + "  " + "-" * val1_width + "  " + "-" * val2_width)
+
+        # Print each difference
+        for diff in differences:
+            key = str(diff['key'])
+            val1 = str(diff['device1_value'])
+            val2 = str(diff['device2_value'])
+
+            # Truncate values if too long
+            if len(val1) > 60:
+                val1 = val1[:57] + "..."
+            if len(val2) > 60:
+                val2 = val2[:57] + "..."
+
+            print(f"{key:<{key_width}}  {val1:<{val1_width}}  {val2:<{val2_width}}")