merge: track H group N

The merge agent stopped this branch on an add/add conflict it had not been
told to expect: groups U and N each created tests/test_understand_tools.py.
Resolved by hand:
- tests/test_understand_tools.py stays U's (the drawing_understand wire
  tests), and N's takeoff wire tests move whole to
  tests/test_understand_takeoff_tools.py. Each file keeps its own client
  fixture: U's opens a fresh document, N's reads files only.
- server.py: SECTION 26 (4 tools, U then D) is kept as merged, and SECTION
  27 (Plant Takeoffs, 2 tools) follows it whole, above the RESOURCES
  banner.
- discovery/aliases.py: additive; the two takeoff records follow the four
  readers.
- tests/test_tool_registry.py: all three branches' paragraphs are kept.
  The snapshot is recomputed from the live registry: analysis 18, 247
  tools. Task 11 ranks `understand` and `plant`.
- docs/tool-inventory.json regenerated (247 tools, 26 groups); README
  counts are 247 registered / 242 advertised. The collected-tests figure
  is left to Task 11.

ruff check passes. Suite: 4919 passed, 1 xfailed. The one deselected test
is the collected-tests figure.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

docs/tool-inventory.json

@@ -3,13 +3,13 @@
   "schema_version": 1,
   "package_version": "1.5.1",
   "totals": {
-    "tools": 245,
+    "tools": 247,
     "resources": 8,
     "prompts": 5,
     "groups": 26
   },
   "groups": {
-    "analysis": 16,
+    "analysis": 18,
     "architecture": 12,
     "batch": 3,
     "blocks": 9,
@@ -543,6 +543,21 @@
         "destructiveHint": false
       }
     },
+    {
+      "name": "cable_takeoff",
+      "group": "analysis",
+      "cost": "safe",
+      "summary": "Cable takeoff: one row per load, Manhattan length to its panel, rounded up to the metre.",
+      "tags": [
+        "analysis",
+        "plant"
+      ],
+      "annotations": {
+        "title": "Plant: Cable Takeoff",
+        "readOnlyHint": false,
+        "destructiveHint": false
+      }
+    },
     {
       "name": "cad_batch",
       "group": "batch",
@@ -2580,6 +2595,21 @@
         "readOnlyHint": true
       }
     },
+    {
+      "name": "pipe_takeoff",
+      "group": "analysis",
+      "cost": "safe",
+      "summary": "Pipe takeoff from a P&ID and its layout: rows by room, service and diameter.",
+      "tags": [
+        "analysis",
+        "plant"
+      ],
+      "annotations": {
+        "title": "Plant: Pipe Takeoff",
+        "readOnlyHint": false,
+        "destructiveHint": false
+      }
+    },
     {
       "name": "plot_style_list",
       "group": "page_setup",