fix: OS release prep - bootstrap script, deps, docs

- Fix bootstrap script (.env.example.local → .env.example)
- Fix @langchain/core version conflict (^1.0.1 → ^0.3.0)
- Add settings:open event listener for LocalKeyGate button
- Pin Next.js to 15.1.3 (was "latest")
- Default runtime to 'local' mode
- Remove desktop app references from UI text
- Rewrite MCP docs for web-only context
- Add SECURITY.md, CODE_OF_CONDUCT.md, CHANGELOG.md
- Add docs/README.md, docs/TROUBLESHOOTING.md
- Update README with platform support table

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/agents/RAHChat.tsx

@@ -503,7 +503,7 @@ export default function RAHChat({
               borderRadius: '6px',
               lineHeight: 1.4
             }}>
-              {quotaError?.message ?? 'Your monthly allowance has been used. Upgrade your plan to keep chatting with RA-H.'}
+              {quotaError?.message ?? 'Rate limit reached. Please wait a moment and try again.'}
             </div>
           )}
           <TerminalInput