docs(i18n): translation capability — style samples, voice rules, two-pass skill

Human-annotated gold pairs land as docs/i18n/style-samples.md (bilingual
by construction, excluded from pairing) and outrank prose tone rules.
translation-rules gains a Voice section; shape stays gate-owned so the
writer optimizes for natural Chinese. The skill's translate step becomes
two passes: native-author writing, then clause-level fidelity check.
Terminology rulings: hash -> 哈希 (blob 哈希/提交哈希), HMR and fiber
confirmed as tabled.

docs/i18n/README.md

@@ -41,7 +41,7 @@ The gate's limit, stated plainly: **a green gate means the pair was confirmed co
 
 - `docs/cordis-catalog/`, `docs/tool-catalog/`, `docs/module-graph.md` — generated files; their generators emit English only today, so a hand-written translation would go stale on every regeneration. The planned follow-up is to teach the generators to emit Chinese alongside English, at which point these leave the exclusion list.
 - `docs/AGENTS.md` — agent instructions, maintained in English only like the root `AGENTS.md`.
-- `docs/i18n/terminology.md` — the terminology table is itself bilingual by construction.
+- `docs/i18n/terminology.md` and [style-samples.md](style-samples.md) — both are bilingual by construction.
 
 **Rollout**: new documents don't wait for a batch — a date-named document (`yyyy-mm-dd-*.md`, i.e. an RFC) dated on or after the manifest's `requiredSince` cutoff must merge with its pair, so everything new is bilingual from birth. Files dated before the cutoff are the grandfathered backlog by definition — including files created on the cutoff's eve — and a document's filename date is its first-proposed date per the RFC convention, so backdating past the cutoff is a review-visible violation, not a loophole. For the back-catalog, the `required` list in the manifest is the enforcement frontier, not the goal. The goal is full bilingual coverage of the scope. Pairs land in reviewable batches (core entry docs, cookbook, RFCs, postmortems, …); each merged batch adds its files to `required`, so the gate ratchets forward and never regresses. Documents not yet in `required` are backlog — visible in `--list` — but any pair that already exists is held to the full contract regardless of the list. Pairing a document is a commitment: every later edit to either side must carry the counterpart along, so grow the frontier at the pace translation review is actually resourced, not ahead of it.