Phase 9: ESL superpowers — Chinese gloss + tone-rewrite

Inline Chinese gloss (offline) and a "say it more naturally" / tone-rewrite,
the two ESL features for the Mandarin-speaking writer.

Gloss: embedded English→Chinese dictionary (gloss.json.gz, 57k common words
built from ECDICT via scripts/build_gloss.py). lexicon gains Gloss()/Result.Gloss
and a lightweight GET /api/gloss/{word}; the right-click WordCard leads with the
中文; GlossTip shows it on a 350ms hover (reuses wordAt, so CJK is never glossed).
Offline + instant, works with the LLM down.

Rewrite: selecting text pops a SelectionBubble (✨更自然 + the tone vocabulary);
picking a style calls POST /api/docs/:id/rewrite (llm.RunRewrite, stateless,
owner-scoped) and shows a RewritePreview (original→rewrite, accept/cancel/retry).
Accept applies it in-editor.

Tests added in lexicon and suggestions. go build/vet/test, tsc, vite all clean;
live smoke vs a fake vLLM verified gloss + rewrite + 400/404/502 paths.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

web/src/components/Editor/GlossTip.tsx

@@ -0,0 +1,32 @@
+// GlossTip is the inline hover gloss: rest the pointer on an English word and a
+// small bubble shows its Chinese meaning, pulled instantly from the offline
+// gloss dataset. It's a pure reading aid — pointer-events are off so it never
+// steals hover or blocks a click, and it sits just under the word. Bilingual
+// chrome elsewhere puts zh first; here the gloss IS the content (the word is
+// already on screen), so the bubble shows only the 中文.
+
+interface Props {
+  gloss: string
+  style: React.CSSProperties
+}
+
+export function GlossTip({ gloss, style }: Props) {
+  return (
+    <div
+      className="petal-gloss-tip pointer-events-none absolute z-20 px-2.5 py-1.5 text-sm"
+      role="tooltip"
+      style={{
+        maxWidth: 280,
+        background: 'var(--color-plum)',
+        color: 'var(--color-surface)',
+        borderRadius: 'var(--radius-input)',
+        boxShadow: 'var(--shadow-soft)',
+        lineHeight: 1.35,
+        fontFamily: "'Nunito','PingFang SC','Microsoft YaHei','Noto Sans CJK SC',sans-serif",
+        ...style,
+      }}
+    >
+      {gloss}
+    </div>
+  )
+}