build: add gemini and xai provider modules
Expands token-monitor with two new provider types:
- providers/gemini.js — Google Gemini API (body-based quota, no headers)
- Probes generateContent endpoint (1 token), falls back gemini-2.0-flash → gemini-2.5-flash
- Parses QuotaFailure violations + RetryInfo from 429 JSON body
- Returns: status, quota_violations[], retry_delay_seconds, severity
- providers/xai.js — x.ai/Grok (OpenAI-compatible header schema)
- Reads x-ratelimit-{limit,remaining}-{requests,tokens} headers
- Handles: no_key, ok, rate_limited, invalid_key states
- Warning threshold: < 10% remaining on requests or tokens
Both providers handle missing API keys gracefully (status: no_key).
Classification via providers/index.js using baseUrl patterns.
140/140 tests passing.
Closes recon findings from trentuna/a-team#91.
Hannibal Smith
1b4e299461
