节点编辑三项增强

- 删除中间节点自动缝合：线性节点删除后把前驱接到其后继
- 撤销/重做：Ctrl+Z / Ctrl+Y（含连线、删除、移动、改字段，防抖快照）
- 开头节点(nodes[0])：绿色边框+「▶开头」标识，选中事件时自动定位到它

web/static/app.js

@@ -81,6 +81,8 @@
     $("graph-empty").style.display = "none";
     ["btn-save", "btn-validate", "btn-playtest", "btn-confirm", "btn-discard", "btn-addnode", "btn-autolayout", "btn-addsucc"].forEach(b => $(b).disabled = false);
     renderAll(true);
+    GraphUI.focusStart(App.ir);     // 定位到开头节点
+    snapReset();                    // 初始化撤销栈
     renderList();
     updateDirty();
   }
@@ -92,8 +94,10 @@
       App.dirty = true; updateDirty();
       if (structural) { GraphUI.render(App.ir, App.selectedNode); FormUI.renderMeta(App.ir, ctx()); FormUI.renderNode(App.ir, App.selectedNode, ctx()); }
       else { GraphUI.updateLabel(App.ir, App.selectedNode); }
+      scheduleSnapshot();
     },
     selectNode: id => { App.selectedNode = id; },
+    deleteNode: id => deleteNode(id),
   });
 
   function selectNode(id) { App.selectedNode = id; GraphUI.select(id); FormUI.renderNode(App.ir, id, ctx()); }
@@ -106,7 +110,7 @@
     App.dirty = true; App.selectedNode = r.id;
     GraphUI.render(App.ir, r.id); FormUI.renderMeta(App.ir, ctx()); FormUI.renderNode(App.ir, r.id, ctx()); updateDirty();
   }
-  // 纯数据删除节点/结局（供右栏删除按钮与画布 Del 键共用）
+  // 纯数据删除节点/结局
   function removeFromIr(id) {
     App.ir.nodes = (App.ir.nodes || []).filter(n => n.id !== id);
     App.ir.endings = (App.ir.endings || []).filter(e => e.id !== id);
@@ -114,6 +118,32 @@
     if (App.selectedNode === id) App.selectedNode = null;
     App.dirty = true; updateDirty();
   }
+  // 线性节点的唯一后继（多出口/结局返回 null，不缝合）
+  function uniqueSuccessor(node) {
+    if (!node) return null;
+    const k = node.kind;
+    if (k === "choice" || k === "choice_once" || k === "random" || k === "fight") return null;
+    if ((App.ir.endings || []).some(e => e.id === node.id)) return null;
+    return node.next || null;
+  }
+  // 把所有指向 from 的跳转改接到 to
+  function retarget(from, to) {
+    (App.ir.nodes || []).forEach(n => {
+      if (n.next === from) n.next = to;
+      if (n.win === from) n.win = to;
+      if (n.lose === from) n.lose = to;
+      (n.options || []).forEach(o => { if (o.goto === from) o.goto = to; if (o.skip && o.skip.node === from) o.skip.node = to; });
+      (n.branches || []).forEach(b => { if (b.goto === from) b.goto = to; });
+    });
+  }
+  // 删除节点：若是线性中间节点，删除后把前驱缝合到它的后继
+  function deleteNode(id) {
+    const node = (App.ir.nodes || []).find(n => n.id === id);
+    const succ = uniqueSuccessor(node);
+    if (succ && succ !== id) retarget(id, succ);
+    removeFromIr(id);
+    renderAll(); scheduleSnapshot();
+  }
   function renderAll() { GraphUI.render(App.ir, App.selectedNode); FormUI.renderMeta(App.ir, ctx()); FormUI.renderNode(App.ir, App.selectedNode, ctx()); }
 
   function updateDirty() {
@@ -252,6 +282,42 @@
     toastTimer = setTimeout(() => el.classList.remove("show"), 2600);
   }
 
+  // ---------- 撤销 / 重做（Ctrl+Z / Ctrl+Y） ----------
+  let undoStack = [], redoStack = [], snapTimer = null;
+  function snapReset() { undoStack = App.ir ? [JSON.stringify(App.ir)] : []; redoStack = []; }
+  function flushSnapshot() {
+    if (!App.ir) return;
+    const cur = JSON.stringify(App.ir);
+    if (!undoStack.length || undoStack[undoStack.length - 1] !== cur) {
+      undoStack.push(cur); if (undoStack.length > 60) undoStack.shift(); redoStack = [];
+    }
+  }
+  function scheduleSnapshot() { clearTimeout(snapTimer); snapTimer = setTimeout(flushSnapshot, 450); }
+  function restoreState(json) {
+    App.ir = JSON.parse(json); App.selectedNode = null; App.dirty = true;
+    renderAll(); updateDirty();
+  }
+  function undo() {
+    flushSnapshot();
+    if (undoStack.length < 2) return;
+    redoStack.push(undoStack.pop());
+    restoreState(undoStack[undoStack.length - 1]);
+    toast("已撤销");
+  }
+  function redo() {
+    if (!redoStack.length) return;
+    const s = redoStack.pop(); undoStack.push(s); restoreState(s);
+    toast("已重做");
+  }
+  document.addEventListener("keydown", e => {
+    if (!(e.ctrlKey || e.metaKey) || !App.ir) return;
+    const a = document.activeElement;
+    if (a && (a.tagName === "INPUT" || a.tagName === "TEXTAREA")) return;   // 输入框内交给浏览器
+    const k = e.key.toLowerCase();
+    if (k === "z" && !e.shiftKey) { e.preventDefault(); undo(); }
+    else if (k === "y" || (k === "z" && e.shiftKey)) { e.preventDefault(); redo(); }
+  });
+
   // ---------- 画布工具栏 ----------
   $("btn-autolayout").onclick = () => {
     if (!App.ir) return;
@@ -267,10 +333,10 @@
   // ---------- 启动 ----------
   GraphUI.init("drawflow", {
     onSelect: id => selectNode(id),
-    onMove: (id, x, y) => { if (!App.ir) return; (App.ir._layout = App.ir._layout || {})[id] = { x: x, y: y }; App.dirty = true; updateDirty(); },
-    onConnect: () => { App.dirty = true; updateDirty(); FormUI.renderNode(App.ir, App.selectedNode, ctx()); },
-    onDisconnect: () => { App.dirty = true; updateDirty(); FormUI.renderNode(App.ir, App.selectedNode, ctx()); },
-    onRemove: id => { removeFromIr(id); FormUI.renderNode(App.ir, App.selectedNode, ctx()); },
+    onMove: (id, x, y) => { if (!App.ir) return; (App.ir._layout = App.ir._layout || {})[id] = { x: x, y: y }; App.dirty = true; updateDirty(); scheduleSnapshot(); },
+    onConnect: () => { App.dirty = true; updateDirty(); FormUI.renderNode(App.ir, App.selectedNode, ctx()); scheduleSnapshot(); },
+    onDisconnect: () => { App.dirty = true; updateDirty(); FormUI.renderNode(App.ir, App.selectedNode, ctx()); scheduleSnapshot(); },
+    onDeleteSelected: id => deleteNode(id),
   });
   (async function () {
     try { const r = await fetch("/api/events?status=all"); if (r.status === 401) { showLogin(); return; } hideLogin(); init(); }