feat(proxy): add /v1/models endpoint for gateway model discovery

[jsboige]

Summary

• Add GET /v1/models endpoint to the proxy server
• Returns all routable models from routing rules, profile model mappings, custom endpoints, and the --model flag
• Enables Claude Code's gateway model discovery (CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY=1)

Details

The endpoint aggregates models from four sources:

1. Routing rules — model name patterns from DEFAULT_ROUTING_RULES + user config (catch-all * excluded)
2. Profile model mappings — opus/sonnet/haiku/subagent role mappings from --model-map or config
3. Custom endpoints — models declared in customEndpoints[].models from ~/.claudish/config.json
4. Default model — the --model flag if set

Response format follows the OpenAI /v1/models convention:

{
  "object": "list",
  "data": [
    { "id": "claude-sonnet-4-20250514", "display_name": "claude-sonnet-4-20250514", "created_at": "..." },
    ...
  ]
}

Zero new dependencies — uses only existing imports (loadConfig, loadRoutingRules). Config read failures for custom endpoints are silently skipped (proxy stays up).

Test plan

• bun run build — compiles without errors
• curl http://localhost:3000/v1/models — returns model list
• With routing rules + custom endpoints configured, verify all models appear
• CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY=1 Claude Code session uses the endpoint correctly

🤖 Generated with Claude Code

Co-Authored-By: Claude Opus 4.7 noreply@anthropic.com