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/api/client.ts

@@ -37,14 +37,21 @@ export interface WordMeaning {
   example?: string
 }
 
-// The offline lookup for one word: a few definition senses and a list of
-// synonyms. Either list may be empty when the word isn't a headword.
+// The offline lookup for one word: a Chinese gloss, a few definition senses, and
+// a list of synonyms. Any of these may be empty when the word isn't a headword.
 export interface WordInfo {
   word: string
+  gloss: string // Chinese translation; '' when the word isn't in the gloss set
   definitions: WordMeaning[]
   synonyms: string[]
 }
 
+// The lightweight Chinese-only gloss behind the inline hover/select tooltip.
+export interface Gloss {
+  word: string
+  gloss: string
+}
+
 export type SuggestionType = 'grammar' | 'phrasing' | 'idiom' | 'clarity' | 'voice'
 
 // A point-in-time snapshot of a document. List responses omit the heavy
@@ -134,8 +141,19 @@ export const api = {
   exportUrl: (id: string, format: ExportFormat) =>
     `/api/docs/${id}/export?format=${format}`,
 
-  // Offline word lookup (definition + synonyms) for the right-click popover.
+  // Offline word lookup (gloss + definition + synonyms) for the right-click popover.
   lookupWord: (word: string) => req<WordInfo>(`/word/${encodeURIComponent(word)}`),
+  // Lightweight Chinese-only gloss for the inline hover/select tooltip — instant
+  // and offline, so it fires on hover without spinning up the heavier lookup.
+  glossWord: (word: string) => req<Gloss>(`/gloss/${encodeURIComponent(word)}`),
+  // Tone-rewrite: rewrites a selected passage in the given style ('natural',
+  // 'academic', …) and returns the rewritten text for an in-editor preview. Not
+  // persisted — the editor applies it directly on accept.
+  rewriteSelection: (docId: string, text: string, style: string) =>
+    req<{ rewrite: string }>(`/docs/${docId}/rewrite`, {
+      method: 'POST',
+      body: JSON.stringify({ text, style }),
+    }),
 
   // Current deployed build id — changes whenever a new frontend ships. The
   // app polls this to offer a refresh. Bypasses any cache so the answer is live.