feat(skills): add i18n-sync skill for agent-driven locale file translation

Adds a community skill that turns the agent into the translation layer
for JSON locale files, delegating the deterministic work (key diffing,
lockfile staleness tracking, placeholder/glossary validation, safe JSON
writes) to the locakit CLI (npm, MIT, zero dependencies).

What makes it different from API-based translation flows:
- No translation API keys or SaaS accounts; the agent itself translates
- The skill instructs the agent to read each key's real usage context
  in the codebase before translating (nav label vs page title vs toast)
- locakit apply rejects keys that don't exist in the source locale,
  containing hallucinated keys
- locakit check gives CI-enforceable validation incl. a Turkish
  language pack (suffix-after-placeholder, dotless-uppercase-i)

Validated end-to-end on a production Next.js 16 portfolio: 175 keys
translated tr->en in one pass, locakit check reporting 0 errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skills/i18n-sync/SKILL.md

@@ -0,0 +1,131 @@
+---
+name: i18n-sync
+description: >
+  Context-aware localization workflow for JSON locale files. Detects missing or
+  stale translation keys with the locakit CLI, reads how each key is used in the
+  codebase to infer real UI context, translates in the project's tone, and writes
+  results back with placeholder/glossary validation. No translation API keys —
+  the agent itself is the translator. Use when adding locale keys, adding a new
+  language, or when the user asks to sync/translate i18n files.
+metadata:
+  origin: community
+---
+
+# i18n Sync
+
+Translate application locale files the way a human localizer would: by looking
+at where each string appears in the product, not just the string itself. The
+deterministic parts (diffing, lockfile tracking, validation, safe JSON writes)
+are delegated to [locakit](https://www.npmjs.com/package/locakit); this skill
+supplies the judgment.
+
+## When to Activate
+
+- New keys were added to the source locale and target languages need catching up
+- A new target language is being introduced
+- Source copy changed and existing translations may be stale
+- The user asks to "translate", "localize" or "sync" locale/i18n JSON files
+- CI failed on `locakit check`
+
+## Requirements
+
+- `locakit.config.json` in the project root (run `npx locakit init` if absent)
+- Locale files matching the config's `files` template, e.g. `locales/{locale}.json`
+
+## Workflow
+
+### 1. Discover pending work
+
+```bash
+npx locakit diff --json
+```
+
+Returns, per target language, every `missing` and `stale` key with its source
+text, plus the project `context` and `glossary` from the config. If empty,
+report that locales are in sync and stop.
+
+### 2. Gather real usage context — the step generic tools skip
+
+For each pending key (batch by feature prefix, e.g. `auth.*`):
+
+- Grep the codebase for the key (`t("auth.welcome.title")`, `$t('auth...')`,
+  `i18nKey="auth..."` and similar forms).
+- Read the surrounding component: is it a button label, a page title, an error
+  toast, an aria-label? Length constraints? Sentence or fragment?
+- Note interpolated values: what will `{name}` actually contain at runtime?
+
+This is what makes "Home" become the navigation label ("Ana Sayfa" in Turkish),
+not the building ("Ev").
+
+### 3. Translate with project tone
+
+Apply, in order of precedence:
+
+1. `glossary` terms from the config — never translate these
+2. `context` from the config — product domain, audience, register (formal
+   "Sie/siz" vs casual "du/sen"); keep the choice consistent across every key
+3. The usage context gathered in step 2 — match UI element type and length
+4. Target-language conventions: preserve all placeholders exactly (`{name}`,
+   `{{count}}`, `%s`, `$t(...)`); keep HTML/Markdown markup intact; follow the
+   language's own punctuation and capitalization rules, not the source's
+
+Language-specific care (examples):
+
+- **Turkish**: avoid apostrophe suffixes after placeholders (`{name}'in` breaks
+  when the value's vowel harmony differs) — rephrase to avoid the suffix.
+  Dotted capital: `i → İ` (GİRİŞ, not GIRIS).
+- **German**: compound nouns can overflow buttons — prefer shorter synonyms for
+  UI controls.
+- **Right-to-left targets** (ar, he, fa): keep placeholders logically ordered;
+  never manually reorder for visual direction.
+
+### 4. Apply and validate
+
+Write the patch as `{ "<lang>": { "<key>": "<translation>" } }` and pipe it in:
+
+```bash
+echo '<patch-json>' | npx locakit apply -
+npx locakit check
+```
+
+`apply` refuses keys that do not exist in the source locale, so a mistyped key
+fails loudly instead of polluting files. `check` enforces placeholder parity,
+glossary retention and language-specific rules; fix any errors it reports and
+re-apply before finishing.
+
+### 5. Report
+
+Summarize per language: how many keys translated, notable tone/terminology
+decisions, and any strings flagged for human review (legal text, marketing
+slogans, culturally sensitive copy — translate them, but say they deserve a
+native speaker's eye).
+
+## Hook Integration (optional)
+
+Trigger a sync reminder whenever the source locale changes:
+
+```json
+{
+  "hooks": {
+    "PostToolUse": [
+      {
+        "matcher": "Write|Edit",
+        "command": "node -e \"const p=process.env.CLAUDE_FILE_PATH||'';if(/locales[\\\\/].*\\.json$/.test(p)){console.log('[i18n-sync] Locale file changed — run locakit diff to check for pending translations.')}\"",
+        "description": "Remind about pending translations after locale edits"
+      }
+    ]
+  }
+}
+```
+
+## Out of Scope
+
+- Extracting hardcoded strings into locale files (separate refactoring task)
+- Non-JSON formats (gettext .po, .strings) — planned in locakit, not yet supported
+- Visual/layout QA of translated UI — see the web testing rules
+
+## Related
+
+- CLI: [locakit on npm](https://www.npmjs.com/package/locakit) — deterministic
+  engine (diff/apply/check/lock); this skill is its intelligence layer
+- Skills: frontend-patterns (UI copy conventions), seo (localized metadata)