feat: add anti-track / anti-upgrade module

[Malkovich-666]

Summary

This PR introduces an Anti-Track / Anti-Upgrade module to crab-code, giving users control over telemetry, version checks, and request sanitization.

What’s added

• crates/api/src/anti_track.rs — New module providing:

  • AntiTrackConfig (exposed from crab_config) with switches for:
    • disable_version_check
    • disable_telemetry
    • disable_update_check
    • block_tracking_domains
    • spoof_version + custom spoofed_version
    • disable_crash_reports
    • disable_feedback
  • sanitize_request() — strips tracking headers (X-Claude-Client-Version, X-Analytics, etc.) and optionally spoofs User-Agent.
  • should_block_url() — blocks known tracking domains (e.g. telemetry.anthropic.com, api.segment.io) and version-check endpoints.
  • Unit tests for domain blocking and header sanitization.

• crates/config/src/settings.rs — Adds AntiTrackConfig struct and anti_track: Option<AntiTrackConfig> to Settings, with proper three-level merge support.

• crates/api/src/lib.rs — Exposes pub mod anti_track and wires settings.anti_track into create_backend().

• crates/api/src/anthropic/client.rs & crates/api/src/openai/client.rs — Integrates anti-track sanitization into every outgoing HTTP request (stream, send, list_models, health_check).

How to use

Add to ~/.crab/settings.json:

{
  "antiTrack": {
    "disableTelemetry": true,
    "disableUpdateCheck": true,
    "blockTrackingDomains": true,
    "spoofVersion": true,
    "spoofedVersion": "1.0.0"
  }
}

Design notes

• The implementation is adapted from the anti-track work in rusty-ai-cli (a Rust rewrite of Claude Code).
• Code analysis, extraction, and porting were assisted by the Hermes Agent.
• The module follows crab-code’s existing crate boundaries (crab_config for settings, crab_api for request sanitization) and keeps API-client changes minimally invasive.

Checklist

• New module with tests
• Config integration
• Anthropic client wired
• OpenAI client wired
• Backward-compatible (defaults to None, no behavior change unless configured)