An edge to a vanished port needs a handle, so the port stays as a ghost (#60)

Four ways erase a derived port and take no edge with them: deleting a state,
deleting the `State machine` literal, deleting `Behavior start`/`end`, deleting
the asset. The common cause is `RemoveNodeCommand` clearing only its own graph,
so the fix sits in `drawnDef` (graph/nested.ts) and touches no delete site.

A right-click on an edge goes through `view.portAt` only — there is no curve
hit-test. Without a port row such an edge is not merely invisible, it is
unreachable, so the ghost row is the handle Disconnect hangs on.

`resolveDef` stays untouched: it is the truth for interpreter, compiler,
ConnectCommand and dropTarget, so nothing runs or connects through a ghost
without a second guard.

tools/e2e/26-state-machine.mjs

@@ -22,6 +22,7 @@ export async function stateMachine(t) {
     has,
     doubleClick,
     drag,
+    mouse,
   } = t;
   const { typeText, undo, redo, world, play, stop } = t;
   const machines = () =>
@@ -273,6 +274,65 @@ export async function stateMachine(t) {
   );
   await shot('03-machine-picked');
 
+  // 26i. A deleted state leaves its edge hanging; the port comes back as a ghost so it can be seen.
+  const named = await states();
+  const nameOf = (id) => named.find((s) => s.id === id)?.name;
+  check(
+    'before the deletion the edge to the second state is drawn',
+    (await json("__gm.graph.edgeDrawn('sm-e4')")) === true,
+  );
+  await mutate(`
+    const m = __gm.state.project.assets.find((x) => x.id === ${JSON.stringify(made.id)});
+    m.graph.nodes = m.graph.nodes.filter((n) => n.id !== ${JSON.stringify(second)});
+  `);
+  await sleep(400);
+  const ghosted = await outputsOf('sm-branch');
+  check(
+    'the deleted state leaves a row named after its key, and takes its name away',
+    names(ghosted).includes(second) && !names(ghosted).includes(nameOf(second)),
+    JSON.stringify({ ghosted, was: nameOf(second) }),
+  );
+  check(
+    'the edge on it is drawn again instead of vanishing',
+    (await json("__gm.graph.edgeDrawn('sm-e4')")) === true,
+  );
+  check(
+    'the node warns about it',
+    (await json("__gm.graph.nodeProblem('sm-branch')")) === '1 edge on a port that is gone',
+    JSON.stringify(await json("__gm.graph.nodeProblem('sm-branch')")),
+  );
+  check(
+    'the ghost pin can be reached, so the edge has a right-click handle',
+    (await json(`__gm.graph.portAt('sm-branch', ${JSON.stringify(second)}, true)`)) !== null,
+  );
+  const pin = await json(`__gm.graph.portAt('sm-branch', ${JSON.stringify(second)}, true)`);
+  const before = await json("__gm.graph.nodeRect('sm-branch')");
+  const links = () => json('__gm.state.project.assets.find((a) => a.id === "sm-logic").graph.edges.length');
+  const linksBefore = await links();
+  // Measured mid-drag: after the release nothing would show either way, because a ghost has no type
+  // and `openPaletteForDrop` gives up on that. The rubber band is the only visible difference.
+  const empty = await json('__gm.graph.emptySpot()');
+  await mouse('mouseMoved', pin.x, pin.y);
+  await mouse('mousePressed', pin.x, pin.y, 'left', {});
+  await mouse('mouseMoved', empty.x, empty.y, 'left', { buttons: 1 });
+  await sleep(150);
+  const dangling = await json('__gm.graph.danglingEdge()');
+  await mouse('mouseReleased', empty.x, empty.y, 'left', {});
+  await sleep(250);
+  const after = await json("__gm.graph.nodeRect('sm-branch')");
+  check(
+    'pressing a ghost pin starts no rubber band, adds no link, and leaves the node where it was',
+    dangling === false && (await links()) === linksBefore && after.x === before.x && after.y === before.y,
+    JSON.stringify({ dangling, linksBefore, links: await links(), moved: after.x - before.x }),
+  );
+  check(
+    'the state that is left keeps its edge and its name',
+    (await json("__gm.graph.edgeDrawn('sm-e3')")) === true &&
+      names(await outputsOf('sm-branch')).includes(nameOf(first)),
+    JSON.stringify({ lines: await outputsOf('sm-branch'), kept: nameOf(first) }),
+  );
+  await shot('04-ghost-port');
+
   // 26h. Everything the step made goes away again.
   const left = await rig.remove();
   await mutate(`