qet-mcp: answer review on naming a conductor by uuid

- An end conductorEnds() reports as "?" is never picked.
- An empty "conductor" says why: an older project's conductors have no
  saved uuid, so qet_conductors reports it empty.
- The op description and README say set_conductor still changes the
  whole potential when given a uuid, and that older projects' conductors
  are named by element + terminal until #1103.
- test_conductor_by_uuid covers move_conductor_segment.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

misc/qet-mcp/README.md

@@ -296,7 +296,12 @@ Python, plus the hang guard on `addConductor` and the database refresh in
   where two conductors meet at a terminal. It is turned at run time into an
   end whose terminal carries only that conductor; where both of its ends
   are shared the op fails and its `note` says why. Needs
-  `qet.conductorEnds()` in the build.
+  `qet.conductorEnds()` in the build. A uuid names one wire, but
+  `set_conductor` still changes the whole potential, the same as by
+  terminal. A project saved before conductors carried a uuid has none in
+  the file: QElectroTech makes a new one on every load and does not save
+  it, so `qet_conductors` reports `uuid` as empty and those conductors are
+  named by `element` + `terminal` until wire uuids last (#1103).
 - **`qet_export` isolates its launch.** SingleApplication keys its socket
   on `applicationFilePath()`, so a second launch of the same binary path
   forwards its request to an already-running instance and returns *that*

misc/qet-mcp/qet_mcp.py

@@ -1419,6 +1419,7 @@ def _build_script(operations: list, output: str) -> str:
         "  if (ends && ends.length === 2) {",
         "    var lines = qet.conductors(folio);",
         "    for (var k = 0; k < 2; k++) {",
+        "      if (ends[k] === '?') continue;",
         "      var n = 0;",
         "      for (var j = 0; j < lines.length; j++) {",
         "        var p = lines[j].split(' : ')[0].split(' -- ');",
@@ -1601,6 +1602,11 @@ def _build_script(operations: list, output: str) -> str:
             if "element" in op or "terminal" in op:
                 raise ValueError(f"operation {i} ({name}): give either \"conductor\" "
                                  f"(its uuid) or \"element\" + \"terminal\", not both")
+            if op["conductor"] == "":
+                raise ValueError(f"operation {i}: \"conductor\" is empty -- a conductor "
+                                 f"from a project saved before conductors carried a uuid "
+                                 f"has none in the file; name it by \"element\" + "
+                                 f"\"terminal\" instead")
             if not isinstance(op["conductor"], str) or not _UUID_RE.fullmatch(op["conductor"]):
                 raise ValueError(f"operation {i}: \"conductor\" must be a conductor uuid, "
                                  f"got {op['conductor']!r}")
@@ -2551,8 +2557,11 @@ TOOLS = [
                         "or give \"conductor\": its uuid from qet_conductors in place "
                         "of \"element\" + \"terminal\" (set_conductor, "
                         "move_conductor_segment and delete_conductor all accept it; it "
-                        "needs one of the conductor's two terminals to carry only it); "
-                        "its \"property\" is one of " + ", ".join(CONDUCTOR_PROPERTIES) +
+                        "needs one of the conductor's two terminals to carry only it, "
+                        "and a conductor qet_conductors lists with an empty uuid has "
+                        "none to give). A uuid names one wire, but set_conductor still "
+                        "changes its whole potential, as it does by terminal. "
+                        "set_conductor's \"property\" is one of " + ", ".join(CONDUCTOR_PROPERTIES) +
                         ". move_conductor_segment reroutes the drawn path itself rather "
                         "than a property of the potential -- addressed the same way (a "
                         "terminal carrying exactly one conductor), plus a segment index "

misc/qet-mcp/test_qet_mcp.py

@@ -206,6 +206,12 @@ class EditValidation(unittest.TestCase):
         s = self.build([{"op": "set_conductor", "folio": 0, "conductor": U,
                          "property": "num", "value": "W1"}])
         self.assertIn('qet.setConductorProperty(0, e0.element, e0.terminal, "num", "W1")', s)
+        s = self.build([{"op": "move_conductor_segment", "folio": 2, "conductor": U,
+                         "segment": 1, "dx": 10, "dy": 0}])
+        self.assertIn(f'var e0 = qetMcpConductorEnd(0, 2, "{U}");', s)
+        self.assertIn("(e0 ? qet.moveConductorSegment(2, e0.element, e0.terminal, 1, 10, 0) : false)", s)
+        # an end whose terminal or element is missing is never picked
+        self.assertIn("if (ends[k] === '?') continue;", s)
         self.assertNotIn('"conductorEnds"', self.build(
             [{"op": "delete_conductor", "folio": 0, "element": U, "terminal": 0}]))
         with self.assertRaisesRegex(ValueError, "not both"):
@@ -213,6 +219,8 @@ class EditValidation(unittest.TestCase):
                          "element": U, "terminal": 0}])
         with self.assertRaisesRegex(ValueError, "must be a conductor uuid"):
             self.build([{"op": "delete_conductor", "folio": 0, "conductor": "W1"}])
+        with self.assertRaisesRegex(ValueError, "saved before conductors carried a uuid"):
+            self.build([{"op": "delete_conductor", "folio": 0, "conductor": ""}])
 
     def test_every_op_generates_a_script(self):
         # one minimal valid instance of every op