docs: bilingual docs contract, translation skill, and pairing gate

Establish EN->ZH bilingual documentation for the README and docs tree:

- docs/i18n/README.md — the pairing contract: sibling foo.md <-> foo.zh.md,
  English canonical, blob-hash source fingerprints, language switchers,
  scope/exclusions, and a manifest-driven rollout ratchet.
- docs/i18n/translation-rules.md — how to translate: faithfulness, structure
  preservation, terminology discipline over docs/i18n/terminology.md, and
  typography rules grounded in MDN/K8s/Vue/clreq conventions.
- .agents/skills/dsh-translate-docs — the committed agent workflow, following
  the dsh-code-review pattern of deferring to docs as sources of truth.
- scripts/verify-translation-pairing.ts + manifest — a doc-sync gate: required
  pairs exist; every existing .zh.md is fresh (fingerprint = current source
  blob), switcher-linked, structure-matched, and non-orphaned; excluded
  (generated) docs stay unpaired. --list prints the translation work list.
- RFC (implemented/process) recording the decision and the alternatives.
- Dogfood: README.zh.md and the two i18n docs translated under their own rules.

Gates: doc-sync green including the new gate; red/green proven for stale
fingerprint, orphan, and excluded-file violations.

docs/rfc/README.md

@@ -141,6 +141,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
 | [Generated cordis events + services catalog](implemented/process/2026-06-20-generated-cordis-catalog.md) | 2026-06-20 |
 | [Classify RFCs by kind via path-encoded subdirectories](implemented/process/2026-06-20-rfc-classification.md) | 2026-06-20 |
 | [Generated tool-schema catalog (boot-and-harvest)](implemented/process/2026-07-02-tool-schema-catalog.md) | 2026-07-02 |
+| [Bilingual documentation via paired sibling files and a pairing gate](implemented/process/2026-07-02-bilingual-docs-and-pairing-gate.md) | 2026-07-02 |
 
 ### Testing