integration-direct: route to MiniMax M3 max-effort instead of Anthropic OAuth

Integration runs were burning the personal Anthropic 5-hour window
(429 storm + window drain, 2026-09-02). New env-only context
minimax-m3-max/v1 pins ANTHROPIC_MODEL=MiniMax-M3[1m], maxes the
thinking budget, and sets the 1M auto-compact window; layered on
minimax/v1 for base URL + apiKeyHelper auth.

Claude-Session: https://claude.ai/code/session_019tJk7P8tZzJ24PvtgoGhLN

harnesses/composites/integration-direct/v1/harness.yaml

@@ -5,7 +5,11 @@ description: "Integration harness — cherry-picks from agent fork and pushes di
 
 layers:
   - context: integration/v1
-  - context: anthropic-cloud-paul-oauth/v1
+  # MiniMax M3 (bulk coding-plan subscription) instead of the Anthropic
+  # personal-subscription OAuth — integration runs are frequent/mechanical
+  # and were draining the interactive 5-hour window (2026-09-02).
+  - context: minimax/v1
+  - context: minimax-m3-max/v1
   - context: gitea-ssh/v1
   - context: agent-repo/v1
   - context: direct-push/v1