Suggestions: right-margin comment rail + Mandarin explanations

Surface every outstanding suggestion as a card in the right-hand
whitespace, vertically aligned to the text it flags — so the writer sees
the whole queue at once instead of hovering each highlight. Cards stack
with collision avoidance, link both ways with their highlight (hover/click
↔ soft text wash, driven through the decoration plugin so it survives
edit repaints), and carry the same Accept / Dismiss / Ask Petal actions.
The rail is a progressive enhancement: it mounts only when there's room
beside the editor, otherwise the existing inline hover card is unchanged.
Stacked cards that reach the bottom-right corner tuck behind the
companion mascot (z-order).

When a card is expanded, the Ask Petal bubble now opens with the
Simplified-Chinese translation of the explanation (the English stays in
the card body) instead of repeating the same text twice — a new
POST /api/suggestions/{id}/translate one-shot LLM endpoint, loaded
lazily on open with an English fallback.

Verified live against the local LLM via the uitest harness: rail
stacking, hover↔text wash, expand/Ask Petal, accept-from-rail, narrow
fallback, and the Mandarin bubble.

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

web/src/components/Editor/SuggestionCard.tsx

@@ -1,15 +1,7 @@
 import { useState } from 'react'
-import type { Suggestion, SuggestionType } from '../../api/client'
+import type { Suggestion } from '../../api/client'
 import { AskPetal } from './AskPetal'
-
-// Per-type accent color + human label, mirroring the design tokens.
-const TYPE_META: Record<SuggestionType, { color: string; label: string }> = {
-  grammar: { color: 'var(--color-mint)', label: 'Grammar' },
-  phrasing: { color: 'var(--color-peach)', label: 'Phrasing' },
-  idiom: { color: 'var(--color-lavender)', label: 'Idiom' },
-  clarity: { color: 'var(--color-sky)', label: 'Clarity' },
-  voice: { color: 'var(--color-honey)', label: 'Voice' },
-}
+import { TYPE_META } from './suggestionMeta'
 
 interface Props {
   suggestion: Suggestion