Editor: document tone, right-click word lookup, expanded stats

Four enhancements to make the editor fit real school usage:

- Per-document tone (academic/professional/casual/humorous/creative/
  persuasive/general): new documents.tone column (migration 0002), threaded
  through the docs API, a bilingual ToneSelect dropdown on the title row, and
  injected into the grammar-checkpoint LLM prompt so advice fits the register.
  The voice pass stays tone-agnostic.

- Right-click word lookup: a new offline `lexicon` package serves definitions
  (Wordset, modern ESL-friendly glosses) and synonyms (WordNet synsets first,
  then frequency+stopword-ranked Moby for breadth) from gzipped embedded data,
  behind /api/word/{word} with light morphology. The WordCard popover shows the
  definition and tappable synonym pills that swap the word in place.

- Expanded writing stats: clicking the word count opens a StatsPanel with page
  count, sentences, paragraphs, reading time, average word length, word variety,
  and Flesch-Kincaid reading level — all computed client-side.

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

web/src/components/Editor/ToneSelect.tsx

@@ -0,0 +1,119 @@
+import { useEffect, useRef, useState } from 'react'
+
+// ToneSelect lets the writer set the document's target tone, which steers the
+// grammar-checkpoint LLM toward the right register (an academic essay vs a casual
+// journal). A small custom dropdown (not a native <select>) so it can carry the
+// bilingual zh·en labels and emoji that match Petal's chrome — the writer uses
+// Mandarin and English. The `value` strings mirror the backend's tone keys.
+
+export interface ToneOption {
+  value: string
+  emoji: string
+  zh: string
+  en: string
+}
+
+// Keep these `value`s in sync with llm.toneGuidance on the server. 'general'
+// means no steering (Petal's default friendly ESL advice).
+export const TONES: ToneOption[] = [
+  { value: 'general', emoji: '🌸', zh: '通用', en: 'General' },
+  { value: 'academic', emoji: '🎓', zh: '学术', en: 'Academic' },
+  { value: 'professional', emoji: '💼', zh: '专业', en: 'Professional' },
+  { value: 'casual', emoji: '☕', zh: '轻松', en: 'Casual' },
+  { value: 'humorous', emoji: '😄', zh: '幽默', en: 'Humorous' },
+  { value: 'creative', emoji: '🎨', zh: '创意', en: 'Creative' },
+  { value: 'persuasive', emoji: '📣', zh: '说服', en: 'Persuasive' },
+]
+
+interface Props {
+  value: string
+  onChange: (value: string) => void
+}
+
+export function ToneSelect({ value, onChange }: Props) {
+  const [open, setOpen] = useState(false)
+  const ref = useRef<HTMLDivElement>(null)
+  const current = TONES.find((t) => t.value === value) ?? TONES[0]
+
+  // Click outside closes the menu.
+  useEffect(() => {
+    if (!open) return
+    const onDown = (e: MouseEvent) => {
+      if (!ref.current?.contains(e.target as Node)) setOpen(false)
+    }
+    document.addEventListener('mousedown', onDown)
+    return () => document.removeEventListener('mousedown', onDown)
+  }, [open])
+
+  return (
+    <div ref={ref} className="relative shrink-0">
+      <button
+        type="button"
+        aria-label="Document tone"
+        aria-haspopup="listbox"
+        aria-expanded={open}
+        onClick={() => setOpen((o) => !o)}
+        className="inline-flex h-9 items-center gap-1.5 whitespace-nowrap px-3 text-sm font-bold"
+        style={{
+          borderRadius: 'var(--radius-pill)',
+          background: 'var(--color-surface)',
+          color: 'var(--color-plum)',
+          boxShadow: 'var(--shadow-soft)',
+        }}
+        title="Set the tone — Petal tailors its advice to match"
+      >
+        <span aria-hidden>{current.emoji}</span>
+        <span>{current.zh}</span>
+        <span style={{ color: 'var(--color-muted)' }}>· {current.en}</span>
+        <span aria-hidden style={{ color: 'var(--color-muted)' }}>
+          ⌄
+        </span>
+      </button>
+
+      {open && (
+        <div
+          role="listbox"
+          className="petal-word-card absolute right-0 z-30 mt-1.5 p-1.5"
+          style={{
+            width: 200,
+            background: 'var(--color-surface)',
+            border: '1px solid var(--color-border)',
+            borderRadius: 'var(--radius-card)',
+            boxShadow: 'var(--shadow-soft)',
+          }}
+        >
+          {TONES.map((t) => {
+            const active = t.value === value
+            return (
+              <button
+                key={t.value}
+                type="button"
+                role="option"
+                aria-selected={active}
+                onClick={() => {
+                  onChange(t.value)
+                  setOpen(false)
+                }}
+                className="flex w-full items-center gap-2 rounded-xl px-2.5 py-1.5 text-left text-sm font-semibold"
+                style={{
+                  background: active ? 'var(--color-surface-alt)' : 'transparent',
+                  color: 'var(--color-plum)',
+                }}
+                onMouseEnter={(e) => (e.currentTarget.style.background = 'var(--color-surface-alt)')}
+                onMouseLeave={(e) =>
+                  (e.currentTarget.style.background = active ? 'var(--color-surface-alt)' : 'transparent')
+                }
+              >
+                <span aria-hidden>{t.emoji}</span>
+                <span>{t.zh}</span>
+                <span className="font-normal" style={{ color: 'var(--color-muted)' }}>
+                  {t.en}
+                </span>
+              </button>
+            )
+          })}
+        </div>
+      )}
+    </div>
+  )
+}