Phase 19: the copy stops being hardcoded Mandarin

Every `中文 · English` string moves out of ~29 components into
web/src/i18n: one Pack type, a verbatim zh pack, and two ways to read
it — usePack() for components, pack() for the modules that build a line
when something happens rather than when something renders.

Anything with a value in it is a function on the pack rather than a
template at the call site, English pluralisation included: word order
isn't universal, and a pack author has to be able to move the number.
The roster constants (tones, rewrite styles, export formats, companions)
keep only value + emoji, so a label can't drift from its key.

On the server, internal/llm/lang.go replaces "Simplified Chinese" in the
three prompts that actually name her language. pt-PT is spelled
"European Portuguese (pt-PT, never Brazilian Portuguese)" in the prompt
itself, and each Lang carries her word for "why" so the tutor prompt
still recognises the question when she asks it her way.

pair_lang reaches the model through the row-scoped query each handler
already ran — the one that proves she owns the document — rather than a
second lookup that could disagree with it.

Also records Phase 18's deploy: migration 0011 rehearsed against a copy
of the live VPS database, then applied for real.

web/src/components/Companion/PetalCompanion.tsx

@@ -4,6 +4,7 @@ import { useCompanion, type Mood } from './useCompanion'
 import { LottiePlayer } from './LottiePlayer'
 import { COMPANIONS, DEFAULT_COMPANION } from './companions'
 import { onPrefsScopeChange, readPref, writePref } from '../../lib/prefs'
+import { usePack } from '../../i18n'
 
 interface Props {
   wordCount: number
@@ -30,6 +31,7 @@ const STORAGE_KEY = 'petal.companion'
 // break reminders. Clicking the mascot opens a picker to switch companions
 // (the choice persists in localStorage).
 export function PetalCompanion({ wordCount, saveStatus, llmDown, editTick, acceptTick, text }: Props) {
+  const t = usePack()
   const { mood, bubble, dismiss, holdBubble, releaseBubble } = useCompanion({
     wordCount,
     saveStatus,
@@ -115,7 +117,7 @@ export function PetalCompanion({ wordCount, saveStatus, llmDown, editTick, accep
             className="px-2 pb-1 pt-0.5 text-[0.7rem] font-bold"
             style={{ color: 'var(--color-muted)' }}
           >
-            选个小伙伴 · Choose a companion
+            {t.companion.choose}
           </p>
           {COMPANIONS.map((c) => {
             const active = c.id === companion.id
@@ -138,7 +140,7 @@ export function PetalCompanion({ wordCount, saveStatus, llmDown, editTick, accep
               >
                 <span style={{ fontSize: 20, lineHeight: 1 }}>{c.emoji}</span>
                 <span className="flex-1">
-                  <span className="font-bold">{c.zh}</span>{' '}
+                  <span className="font-bold">{t.companion.names[c.id] ?? c.name}</span>{' '}
                   <span style={{ color: 'var(--color-muted)' }}>{c.name}</span>
                 </span>
                 {active && <span style={{ color: 'var(--color-accent)' }}>✓</span>}
@@ -169,7 +171,7 @@ export function PetalCompanion({ wordCount, saveStatus, llmDown, editTick, accep
             className="font-bold leading-snug"
             style={{ color: 'var(--color-plum)', fontSize: '1.4rem' }}
           >
-            {bubble.zh}
+            {bubble.native}
           </p>
           <p
             className="mt-0.5 leading-snug"