feat(i18n): introduce internationalization architecture and zh-CN support

This commit adds a robust i18n framework to OpenClaw with the following highlights:

1. Non-invasive Architecture: The core logic remains untouched. The i18n layer acts as a lightweight UI wrapper, ensuring zero side effects on the agent's performance or stability.
2. Seamless Migration: 100% backward compatible. Existing users will notice no change unless the LANG environment variable is explicitly set.
3. Robust Fallback: Implements a reliable fallback mechanism that defaults to English strings if a translation is missing or corrupted.
4. Onboarding Focus: Prioritizes the onboarding wizard and skill descriptions to improve accessibility for Chinese-speaking users.

Changes:
- Implemented a unified t() translation helper.
- Added locales/en.ts (base) and locales/zh.ts.
- Enabled language switching via LANG/LC_ALL environment variables.
- Added comprehensive documentation in i18n/README.md.

Testing: Lightly tested with LANG=zh_cn environment variable
Prompts: Used Claude 3.5 for translation assistance

scripts/extract-skill-descriptions.js

@@ -0,0 +1,98 @@
+#!/usr/bin/env node
+
+import fs from 'fs';
+import path from 'path';
+
+const skillsDir = path.join(process.cwd(), 'skills');
+
+function extractSkillDescription(skillDir) {
+  const skillFile = path.join(skillDir, 'SKILL.md');
+  if (!fs.existsSync(skillFile)) {
+    return null;
+  }
+  
+  const content = fs.readFileSync(skillFile, 'utf8');
+  const frontmatterMatch = content.match(/^---[\s\S]*?---/);
+  if (!frontmatterMatch) {
+    return null;
+  }
+  
+  const frontmatter = frontmatterMatch[0];
+  const descriptionMatch = frontmatter.match(/description:\s*([^\n]+)/);
+  if (!descriptionMatch) {
+    return null;
+  }
+  
+  const description = descriptionMatch[1].trim().replace(/^"|"$/g, '');
+  const metadataMatch = frontmatter.match(/metadata:\s*({[^}]+})/);
+  let installLabel = null;
+  
+  if (metadataMatch) {
+    try {
+      const metadata = JSON.parse(metadataMatch[1]);
+      if (metadata.openclaw && metadata.openclaw.install && metadata.openclaw.install[0]) {
+        installLabel = metadata.openclaw.install[0].label;
+      }
+    } catch (e) {
+      // Ignore parsing errors
+    }
+  }
+  
+  return { description, installLabel };
+}
+
+function main() {
+  const skillDescriptions = [];
+  
+  if (!fs.existsSync(skillsDir)) {
+    console.error('Skills directory not found');
+    process.exit(1);
+  }
+  
+  const skillNames = fs.readdirSync(skillsDir);
+  
+  for (const skillName of skillNames) {
+    const skillDir = path.join(skillsDir, skillName);
+    if (fs.statSync(skillDir).isDirectory()) {
+      const result = extractSkillDescription(skillDir);
+      if (result && result.description) {
+        skillDescriptions.push({
+          name: skillName,
+          description: result.description,
+          installLabel: result.installLabel
+        });
+      }
+    }
+  }
+  
+  console.log('Extracted skill descriptions:');
+  console.log('================================');
+  
+  const translationEntries = [];
+  
+  for (const skill of skillDescriptions) {
+    console.log(`Skill: ${skill.name}`);
+    console.log(`Description: ${skill.description}`);
+    if (skill.installLabel) {
+      console.log(`Install Label: ${skill.installLabel}`);
+    }
+    console.log('--------------------------------');
+    
+    translationEntries.push(`  '${skill.description.replace(/'/g, "\\'")}': '${skill.description}',`);
+    if (skill.installLabel) {
+      translationEntries.push(`  '${skill.installLabel.replace(/'/g, "\\'")}': '${skill.installLabel}',`);
+    }
+  }
+  
+  console.log('\nTranslation entries (add to src/i18n/locales/zh_CN.ts):');
+  console.log('==================================================');
+  console.log(translationEntries.join('\n'));
+  
+  console.log(`\nTotal skills found: ${skillDescriptions.length}`);
+}
+
+if (import.meta.url === `file://${process.argv[1]}`) {
+  main();
+}
+
+export { extractSkillDescription, main };