Fix Antigravity Windows discovery

[ozymandiashh]

Summary

Fixes Antigravity usage discovery on Windows by teaching the provider to find Windows language-server processes and parse the Windows extension-server flags.

What changed

• discover Antigravity language-server command lines via Get-CimInstance Win32_Process on Windows
• keep POSIX discovery, but use ps -ww -eo args to avoid truncated command lines
• parse both legacy flags and Windows flags:
  • --https_server_port
  • --csrf_token
  • --extension_server_port
  • --extension_server_csrf_token
• support both --flag value and --flag=value, including quoted values
• handle both wrapped and unwrapped Connect-RPC response payloads for model maps and generator metadata
• add focused unit coverage for process parsing and RPC response extraction
• update provider docs and changelog

Closes #249.

Validation

• npx vitest run tests/providers/antigravity.test.ts — 11 tests passed
• npx vitest run — 50 files / 695 tests passed
• npm run build — passed
• git diff --check — passed
• Claude Opus 4.7 effort=max external review — approved, no required fixes
• Gemini 3.1 Pro Preview external review — PASS, no required fixes

Notes

npx tsc --noEmit currently fails on src/models-report.ts:151 (Type 'string' is not assignable to type 'TaskCategory'). That file is untouched by this PR; the line is from existing main history.