Add Claude Code network diagnostics

[jacklv-coder]

Summary

• add first-class Claude Code and Anthropic-compatible gateway diagnostics alongside Codex
• auto-detect safe routing/model configuration, including Alibaba Cloud Model Studio/DashScope and deepseek-v4-flash
• report per-client TTFB, jitter, reachability, proxy behavior, and stable JSON output
• harden privacy boundaries by ignoring .curlrc, rejecting credential-bearing endpoints, constraining protocols, and never attaching API authentication
• add release automation, ShellCheck CI, bilingual documentation, security policy, contribution guides, and issue templates
• explicitly defer npm distribution; v0.3.0 will ship through GitHub Releases and Homebrew

Why

Developers behind proxies need a repeatable answer to whether Codex or Claude Code is slow, blocked, or using the wrong gateway. The previous version only understood Codex/OpenAI paths and could not validate Claude-compatible routes.

Verification

• bash -n bin/ipcheck test/smoke.sh
• bash test/smoke.sh
• YAML parsing for workflows, Dependabot, and issue templates
• real unauthenticated DashScope /v1/messages probe: HTTP 403, reachable, approximately 274 ms TTFB
• three GPT-5.6 Luna review passes; final result: no P1/P2 findings

Release scope

After CI passes, merge and tag v0.3.0, then update jacklv-coder/homebrew-tap. npm publishing is intentionally deferred.