Describe the bug

When using the opencode zen GLM 4.7 model, it triggers a "Message ordering conflict" error that corrupts the session in a way that causes ALL models to fail until a full reset is performed.

Steps to reproduce

1. Use opencode zen GLM 4.7 model
2. Session runs for a while (sometimes after debugging loops or other issues)
3. Suddenly all messages return: "Message ordering conflict - please try again. If this persists, use /new to start a fresh session."
4. Critical: Even after using /new, /reset, or clawdbot /new, the error persists
5. All other models also fail with the same error
6. Only a full reset fixes it (see Workaround)

Expected behavior

• Model should handle message ordering correctly
• Session reset commands (/new, /reset) should recover from corrupted state
• Corrupted session should be isolated to the problematic model/provider

Actual behavior

• opencode zen GLM 4.7 triggers message ordering conflict
• Error spreads to ALL models (not just the problematic one)
• /new, /reset, and clawdbot /new don't recover the session
• Complete reset required

Workaround (to recover)

1. Delete all session files from ~/.clawdbot/sessions/
2. Restart the clawdbot gateway completely (not just hot reload)
3. Start a new session with a DIFFERENT model (e.g., z.ai coding plan GLM 4.7)

Environment

• Problematic model: opencode zen GLM 4.7
• Working model with same base: z.ai coding plan GLM 4.7
• Other models: Work fine after recovery
• Error source: src/agents/pi-embedded-helpers/errors.ts (lines 198-201) - triggered by LLM returning "incorrect role information" or "roles must alternate"

Additional notes

• The same GLM 4.7 model from z.ai provider works without issues
• This isolates the bug to the opencode provider's implementation
• The session corruption shouldn't cascade to other models - suggests session state isn't properly isolated per-provider