Phase 0: Switch operators to Sonnet 4.6 (CLAUDE_CODE_SUBAGENT_MODEL) #102

Phase 0: Switch operators to Sonnet 4.6

Context: Comms architecture plan calls for operators to run on Sonnet 4.6 instead of Opus. SWE-bench gap is 1.2 points (80.8% vs 79.6%) at 5x cost savings. Sonnet has its own independent weekly bucket since November 2025.

Scope:

• Set CLAUDE_CODE_SUBAGENT_MODEL=claude-sonnet-4-6 in clide container config
• Verify Sonnet subagent model works correctly in Claude Code sessions
• Document which operators stay on Opus (Boss, Lead) vs switch to Sonnet (all builders)
• Monitor for any quality regressions in first week

Implementation:

• Add CLAUDE_CODE_SUBAGENT_MODEL to docker-compose env or entrypoint
• May also need CLAUDE_MODEL override per-operator if operators should default to Sonnet for their main session (not just subagents)
• Boss and Lead windows should remain on Opus — need per-window model selection or separate container config

Acceptance criteria:

• Environment variable set in clide container
• At least one operator session verified running on Sonnet
• Opus usage for Boss/Lead confirmed unaffected
• Billing impact observable (Sonnet bucket usage appears)

Part of: Clidecorral Phase 0 — Foundations
Refs: /workspace/workspace/planning/comms-architecture-plan.md, Google/MIT study (arXiv:2512.08296)