fix: Add macOS support for KiCad bundled Python detection

Adds macOS-specific detection for KiCad's bundled Python, eliminating manual
PYTHONPATH configuration for macOS users.

Changes:
- Detects KiCad bundled Python at standard macOS install path (Python 3.9-3.12)
- Makes KICAD_PYTHON environment variable cross-platform (not just Windows)
- Adds logging for Python detection to aid debugging
- Updates documentation with simplified macOS setup (no PYTHONPATH needed)

Fixes server startup on macOS where existsSync('python3') was failing validation
because it doesn't check PATH.

Based on PR #18 by @hexatriene - applied manually due to merge conflict with
router implementation. Full credit to hexatriene for the solution design and
implementation.

Co-authored-by: hexatriene <106840313+hexatriene@users.noreply.github.com>

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/CLIENT_CONFIGURATION.md

@@ -46,17 +46,29 @@ This guide shows how to configure the KiCAD MCP Server with various MCP-compatib
   "mcpServers": {
     "kicad": {
       "command": "node",
-      "args": ["/Users/YOUR_USERNAME/MCP/KiCAD-MCP-Server/dist/index.js"],
-      "env": {
-        "PYTHONPATH": "/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/lib/python3.11/site-packages",
-        "NODE_ENV": "production"
-      }
+      "args": ["/Users/YOUR_USERNAME/MCP/KiCAD-MCP-Server/dist/index.js"]
     }
   }
 }
 ```
 
-**Note:** Adjust Python version (3.11) and KiCAD path based on your installation.
+**Note:** For standard KiCad installations in `/Applications/KiCad/`, the server auto-detects KiCad's bundled Python (versions 3.9-3.12). No `PYTHONPATH` configuration is required.
+
+If KiCad is installed in a non-standard location, you can override the Python path:
+
+```json
+{
+  "mcpServers": {
+    "kicad": {
+      "command": "node",
+      "args": ["/Users/YOUR_USERNAME/MCP/KiCAD-MCP-Server/dist/index.js"],
+      "env": {
+        "KICAD_PYTHON": "/custom/path/to/python3"
+      }
+    }
+  }
+}
+```
 
 ### Windows Configuration