feat: add find_orphaned_wires schematic analysis tool

Detects wire segments with at least one dangling endpoint — an endpoint
not connected to a component pin, net label, or another wire.  These
cause ERC 'wire end unconnected' violations and are a common symptom of
incomplete routing or stray stub wires.

Algorithm uses exact KiCad IU (10 000 IU/mm) coordinate matching,
consistent with wire_connectivity.py:
  1. Build an endpoint-frequency map for all wires (IU precision)
  2. Collect anchored IU points: component pins (via PinLocator),
     net labels / global_labels, power symbol pins
     (via _parse_virtual_connections)
  3. An endpoint is dangling when it is touched by exactly one wire AND
     is not an anchored point; the containing wire is reported

Does not require the KiCad UI to be running.

Changes:
  python/commands/schematic_analysis.py — find_orphaned_wires() function
  python/kicad_interface.py             — handler + route registration
  python/schemas/tool_schemas.py        — MCP schema entry
  src/tools/schematic.ts                — TypeScript server.tool() call
  tests/test_schematic_analysis.py      — 7 integration tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

python/schemas/tool_schemas.py

@@ -1794,6 +1794,26 @@ SCHEMATIC_TOOLS = [
             "required": ["schematicPath"],
         },
     },
+    {
+        "name": "find_orphaned_wires",
+        "title": "Find Orphaned Wires",
+        "description": (
+            "Find wire segments with at least one dangling endpoint — an endpoint not connected "
+            "to a component pin, net label, or another wire. "
+            "Orphaned wires cause ERC 'wire end unconnected' errors and indicate routing mistakes. "
+            "Does not require the KiCad UI to be running."
+        ),
+        "inputSchema": {
+            "type": "object",
+            "properties": {
+                "schematicPath": {
+                    "type": "string",
+                    "description": "Path to the .kicad_sch schematic file",
+                }
+            },
+            "required": ["schematicPath"],
+        },
+    },
 ]
 
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