feat(pid): pid_graph reads the drawing back with ports, junctions, dangling ends and confidence

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

docs/tool-inventory.json

@@ -3,7 +3,7 @@
   "schema_version": 1,
   "package_version": "1.5.1",
   "totals": {
-    "tools": 160,
+    "tools": 161,
     "resources": 6,
     "prompts": 5,
     "groups": 20
@@ -21,7 +21,7 @@
     "entity_query": 9,
     "layers": 14,
     "layouts": 12,
-    "pid": 3,
+    "pid": 4,
     "premium": 12,
     "solids": 5,
     "system": 7,
@@ -1717,6 +1717,20 @@
         "readOnlyHint": false
       }
     },
+    {
+      "name": "pid_graph",
+      "group": "pid",
+      "cost": "read",
+      "summary": "Read the P&ID back as a graph: symbols, lines, junctions, dangling ends, confidence.",
+      "tags": [
+        "pid",
+        "query"
+      ],
+      "annotations": {
+        "title": "P&ID: Connectivity Graph",
+        "readOnlyHint": true
+      }
+    },
     {
       "name": "pid_line_draw",
       "group": "pid",