feat(i18n): add @fusion/i18n package, catalogs, and i18next-cli tooling (U2)

Create the @fusion/i18n package as the authored source-of-truth: shared
i18next config (namespace split, script-aware zh-CN/zh-TW fallback, plural
setup), en base catalogs, and a generated CLI static-import map so the
terminal surface is drop-in for new locales. Add the i18next-cli workflow
(extract/sync/types/status/lint) wired as root i18n:* scripts, install the
i18next stack into dashboard + CLI, strip @fusion/i18n from the published CLI
manifest, gitignore the generated dashboard catalog tree, and add a changeset.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/cli/package.json

@@ -59,13 +59,15 @@
     "@earendil-works/pi-coding-agent": "^0.78.0",
     "dockerode": "^4.0.12",
     "express": "^5.1.0",
+    "i18next": "^26.3.1",
     "ink": "^6.8.0",
     "ink-spinner": "^5.0.0",
     "ink-text-input": "^6.0.0",
     "ioredis": "^5.6.0",
     "multer": "^2.1.1",
     "node-pty": "npm:@homebridge/node-pty-prebuilt-multiarch@^0.13.1",
-    "react": "^19.0.0"
+    "react": "^19.0.0",
+    "react-i18next": "^17.0.8"
   },
   "peerDependencies": {
     "@earendil-works/pi-ai": "*",
@@ -87,6 +89,7 @@
     "@fusion/core": "workspace:*",
     "@fusion/dashboard": "workspace:*",
     "@fusion/engine": "workspace:*",
+    "@fusion/i18n": "workspace:*",
     "@fusion/pi-claude-cli": "workspace:*",
     "@fusion/pi-llama-cpp": "workspace:*",
     "@types/node": "^22.0.0",