System prompt leak in compact command failure

Issue Description

When the claude --compact command fails, it appears to leak internal system prompts in the error output. This is a security/privacy concern as system prompts may contain internal implementation details that shouldn't be exposed to users.

Steps to Reproduce

1. Run claude -p "..." --resume "session-id" with compact functionality
2. Command fails with exit code 1
3. System prompt content is visible in the error output

Security Impact

• Exposes internal system prompt instructions
• May reveal implementation details not intended for user visibility
• Could be used to understand/exploit prompt engineering patterns

Expected Behavior

Error messages should be sanitized and contain only user-appropriate information without exposing internal system prompts.

Actual Behavior

Full system prompt content is leaked in error output when compact command fails.