xint-phased-credential-model-three-tiers

xint capabilities are gated by credential availability across three phases: Phase 1 (xAI API key only, already available) unlocks 15+ capabilities including x_search, analyze, report, article extraction, and xAI Collections. Phase 2 (+ X Bearer Token) unlocks direct X API v2 read ops: search with exact metrics, profile, tweet, thread, trends, watch, stream, media. Phase 2b (+ OAuth 2.0 Client ID) unlocks write/engagement ops: like, bookmark, follow, engage (AI growth engine), analytics, timing heatmaps. System should auto-detect available credentials and expose only valid commands.