feat(i18n): briefing generator and pair-scoped pairing gate

gen-translation-brief assembles the minimal-update working set for an
out-of-sync pair from its consistency record: the authored side's diff
since last confirmation, the counterpart sections that diff lands in
(heading-mapped only where the last-confirmed structures align), the
terminology rows the diff touches, and a per-direction rules digest.

verify-translation-pairing now accepts pair paths to check just the
named pairs during update iteration; --write requires naming the
confirmed pairs (--write --all is the explicit corpus form) so a bulk
re-record can no longer silently bless drifted pairs the caller never
reviewed. Each record's comment names its own scoped command.

package.json

@@ -56,6 +56,7 @@
     "verify-type-equiv": "tsx scripts/verify-type-equiv.ts",
     "verify-translation-prompt": "tsx scripts/verify-translation-prompt.ts",
     "verify-translation-pairing": "tsx scripts/verify-translation-pairing.ts",
+    "gen-translation-brief": "tsx scripts/gen-translation-brief.ts",
     "verify-doc-budgets": "tsx scripts/verify-doc-budgets.ts",
     "docs:dev": "pnpm --filter @deepseek-ai/website run dev",
     "docs:build": "pnpm --filter @deepseek-ai/website run build",