xint-mcp-policy-tiers-must-match-credential-phases

xint MCP registration uses read_only policy for Phase 1 and Phase 2 (no write operations possible without OAuth). Phase 2b engagement/write commands require an engagement policy tier. Registering with read_only when OAuth credentials are present silently blocks all write-capable tools. The MCP .mcp.json entry must be updated alongside credential activation when advancing phases.