feat: set custom User-Agent header for API requests

[chingjustwe]

feat: set custom User-Agent header for API requests

Problem

When using deepcode-cli with custom/proxy API endpoints routed through Cloudflare or strict enterprise WAFs, requests fail with 403 Forbidden. The root cause is that the OpenAI SDK sends User-Agent: OpenAI/JS x.x.x by default, which proxy operators commonly block via WAF rules to prevent abuse of their OpenAI relay services.

Changes

1. New src/common/package-info.ts — central place that reads package.json once and exports APP_NAME and APP_VERSION as shared constants.

2. src/common/openai-client.ts — override the User-Agent in the custom fetch wrapper from OpenAI/JS 6.35.0 to deepcode-cli/${version} (e.g. deepcode-cli/0.1.27). This references the same pattern as opencode: opencode/${version}.

3. src/cli.tsx — use the shared APP_NAME / APP_VERSION from package-info.ts instead of local require("../package.json").

Verification

• deepcode --version outputs the correct version
• All 410 tests pass
• TypeScript typecheck, ESLint, Prettier all pass
• Build (npm run build) succeeds

Related Issue

#177