Add Roo Code context sync: .clinerules symlink and sync script

- Add .clinerules symlink → CLAUDE.md so Roo Code reads same project context
- Add sync-context.sh: copies global context to ~/.claude/ for Claude Code
  and prints content for manual paste into Roo Code Custom Instructions
- Update CLAUDE.md: note .clinerules symlink, add sync-context.sh to file list
- Update CONTEXT.md: add AI context file mapping table, update file structure
- Update README.md: rewrite AI Context Files section to cover both tools,
  document symlink strategy and sync workflow

CLAUDE.md

@@ -1,6 +1,7 @@
 # Ein AI Proxy - Project Context
 
 Anthropic-compatible proxy that routes AI requests to multiple providers based on model name: sonnet→GLM-4.7 (Z.ai), opus→Anthropic, haiku→DeepSeek.
+`.clinerules` is a symlink to this file so Roo Code reads the same context.
 
 ## File Structure
 - `proxy.mjs` - Main proxy server (zero dependencies, Node.js built-ins only)
@@ -8,6 +9,7 @@ Anthropic-compatible proxy that routes AI requests to multiple providers based o
 - `config.example.json` - Template config
 - `ein-ai-proxy.service` - Systemd unit file
 - `deploy.sh` - Deployment and testing script
+- `sync-context.sh` - Syncs global context to Claude Code and Roo Code
 
 ## Development
 Run locally: `node proxy.mjs` (requires `config.json`)