feat: 垂懸字避免（方案 C，斷行層無測量，order 70）（§6.5.1）

段末行 CJK 實義字數 ≥ N（預設 2；標點／符號不計）。standalone 段落級 pass：
自段末向前數 N 個實義字，把「第 N 字起至段末」（含其間／尾隨標點）包入
<jz-orphan>（white-space:nowrap）。該整體不可斷 → 末行恒含之 ⇒ 末行實義字 ≥ N，
任意寬度／字型／瀏覽器成立，無需量測 layout。

要點：
- 邊界字定位跨 jz-jinze／行內元素攀爬：實義字落於行內元素內時綁定整個塊級
  直接子（不切割 nowrap 群、revert 乾淨）；僅裸文本直接子才精確切分（最小綁定）。
- 僅處理葉段落（無塊級後代）；段落實義字 < N 不綁；單行段方案 C 本就無害。
- 選項 orphan?: boolean | { chars? }；**預設開 chars=2**（§6.5.6 建議）；
  下游可 orphan:false 關閉。段落級，data-jz-level=text 子樹自動跳過。
- order=70：jinze(40)／spacing(50)／longWord(60) 後、layout pass(90/92) 前。

新增 _orphan.css（jz-orphan{white-space:nowrap}）；JzTag 加 jz-orphan。
9 項單元測試（末 N＋尾標點、chars 選項、標點不計、實義字<N 不綁、跨 jinze、
關閉、冪等、revert、段落級閘）。共 85 測試全綠。

窄容器拖動「末行恒 ≥N」之 layout 驗證留待 demo（Step 4-5，瀏覽器）。

dist/juzhen.iife.js

@@ -1192,8 +1192,106 @@ var Juzhen = (() => {
     }
   };
 
+  // src/typeset/orphan.ts
+  var PASS4 = "orphan";
+  function hasOrphan(block) {
+    for (let c = block.firstChild; c; c = c.nextSibling) {
+      if (c.nodeType === 1 && c.nodeName === "JZ-ORPHAN") {
+        return true;
+      }
+    }
+    return false;
+  }
+  function collectSubst(block, finder, blockSet, anyCjk, biaodian) {
+    const out = [];
+    const visit = (node, directChild) => {
+      if (node.nodeType === 3) {
+        const t = node;
+        const d = t.data;
+        for (let i = 0; i < d.length; i += 1) {
+          const ch = d.charAt(i);
+          if (anyCjk.test(ch) && !classifyBiaodian(ch, biaodian)) {
+            out.push({ directChild, textNode: t, offset: i });
+          }
+        }
+        return;
+      }
+      if (node.nodeType !== 1) {
+        return;
+      }
+      const el = node;
+      if (finder.isAvoided(el)) {
+        return;
+      }
+      if (blockSet.has(el.nodeName) || finder.pillMatches(el)) {
+        return;
+      }
+      for (let c = el.firstChild; c; c = c.nextSibling) {
+        visit(c, directChild);
+      }
+    };
+    for (let dc = block.firstChild; dc; dc = dc.nextSibling) {
+      visit(dc, dc);
+    }
+    return out;
+  }
+  function processBlock(block, finder, blockSet, anyCjk, biaodian, chars) {
+    if (hasOrphan(block)) {
+      return;
+    }
+    const subst = collectSubst(block, finder, blockSet, anyCjk, biaodian);
+    if (subst.length < chars) {
+      return;
+    }
+    const boundary = subst[subst.length - chars];
+    let startChild = boundary.directChild;
+    if (boundary.textNode && boundary.textNode === startChild) {
+      if (boundary.offset > 0) {
+        startChild = boundary.textNode.splitText(boundary.offset);
+      }
+    }
+    const orphan = createJz("jz-orphan", PASS4, "wrap");
+    block.insertBefore(orphan, startChild);
+    let n = startChild;
+    while (n) {
+      const next = n.nextSibling;
+      orphan.appendChild(n);
+      n = next;
+    }
+  }
+  var orphanPass = {
+    name: PASS4,
+    kind: "standalone",
+    order: 70,
+    level: "paragraph",
+    enabled: (o) => o.features.orphan,
+    render(ctx) {
+      const { finder, options } = ctx;
+      const blockSet = options.finder.blockTags;
+      const anyCjk = new RegExp("[" + options.ruleset.cjk + "]");
+      const biaodian = options.ruleset.biaodian;
+      const chars = options.orphan.chars;
+      finder.eachBlock(ctx.root, (block) => {
+        if (!finder.levelAllows(block, "paragraph")) {
+          return;
+        }
+        if (!finder.featureEnabledFor(block, PASS4)) {
+          return;
+        }
+        const sel = Array.from(blockSet).map((t) => t.toLowerCase()).join(",");
+        if (sel && block.querySelector(sel)) {
+          return;
+        }
+        processBlock(block, finder, blockSet, anyCjk, biaodian, chars);
+      });
+    },
+    revert(ctx) {
+      revertPass(PASS4, ctx.root);
+    }
+  };
+
   // src/typeset/spacing.ts
-  var PASS4 = "spacing";
+  var PASS5 = "spacing";
   var MARK = "\uE000";
   var PH_OPEN = "\uE001";
   var PH_CLOSE = "\uE002";
@@ -1294,7 +1392,7 @@ var Juzhen = (() => {
     if (!parent || parent.nodeName === "JZ-HWS") {
       return;
     }
-    const gap = createJz("jz-hws", PASS4, "wrap");
+    const gap = createJz("jz-hws", PASS5, "wrap");
     parent.insertBefore(gap, node);
     gap.appendChild(node);
   }
@@ -1311,7 +1409,7 @@ var Juzhen = (() => {
     }
     wrapNodeInGap(tn);
   }
-  function processBlock(block, finder, R) {
+  function processBlock2(block, finder, R) {
     const runs = finder.collectRuns(block);
     for (const run of runs) {
       const { text, map } = run;
@@ -1403,7 +1501,7 @@ var Juzhen = (() => {
     }
   }
   var spacingPass = {
-    name: PASS4,
+    name: PASS5,
     kind: "standalone",
     order: 50,
     level: "text",
@@ -1412,18 +1510,18 @@ var Juzhen = (() => {
       const { finder, options } = ctx;
       const R = makeRules(options.ruleset);
       ctx.finder.eachBlock(ctx.root, (block) => {
-        if (!finder.featureEnabledFor(block, PASS4)) {
+        if (!finder.featureEnabledFor(block, PASS5)) {
           return;
         }
-        processBlock(block, finder, R);
+        processBlock2(block, finder, R);
       });
-      if (!options.finder.blockTags.has(ctx.root.nodeName) && finder.featureEnabledFor(ctx.root, PASS4) && finder.inScope(ctx.root) && !finder.isAvoided(ctx.root)) {
-        processBlock(ctx.root, finder, R);
+      if (!options.finder.blockTags.has(ctx.root.nodeName) && finder.featureEnabledFor(ctx.root, PASS5) && finder.inScope(ctx.root) && !finder.isAvoided(ctx.root)) {
+        processBlock2(ctx.root, finder, R);
       }
       processPills(ctx.root, finder, options.finder.pillSelector, R.pillNeighbor);
     },
     revert(ctx) {
-      revertPass(PASS4, ctx.root);
+      revertPass(PASS5, ctx.root);
     }
   };
 
@@ -1576,6 +1674,7 @@ var Juzhen = (() => {
     longWordPass,
     spacingPass,
     jinzePass,
+    orphanPass,
     lineEdgePass,
     gapTrimPass
   ];
@@ -1593,6 +1692,13 @@ var Juzhen = (() => {
     const lang = typeof v.lang === "string" && v.lang ? v.lang : "en";
     return { minLength, lang };
   }
+  function resolveOrphan(v) {
+    if (v && typeof v === "object") {
+      const chars = typeof v.chars === "number" && v.chars >= 1 ? Math.floor(v.chars) : 2;
+      return { chars };
+    }
+    return { chars: 2 };
+  }
   function resolveJiya(v) {
     if (v && typeof v === "object") {
       return {
@@ -1625,12 +1731,14 @@ var Juzhen = (() => {
         longWord: opts.longWord === false ? false : feature(opts.longWord, true),
         jiya: feature(opts.jiya, true),
         jinze: feature(opts.jinze, true),
+        orphan: opts.orphan === false ? false : feature(opts.orphan, true),
         hanging: feature(opts.hanging, false),
         biaodian: feature(opts.biaodian, false),
         emphasis: feature(opts.emphasis, false),
         ruby: feature(opts.ruby, false)
       },
       longWord: resolveLongWord(opts.longWord),
+      orphan: resolveOrphan(opts.orphan),
       jiyaConfig: resolveJiya(opts.jiya),
       blocks: Array.isArray(opts.blocks) ? opts.blocks.slice() : [],
       finder: {