No auto-compact or guidance when hitting 20MB request limit

When a conversation exceeds 20MB, every request fails repeatedly with 'Request too large (max 20MB)' and no recovery path. There's no auto-compact and no suggestion to run /compact. The user is stuck until they manually figure out to compact.

Expected behavior: Claude Code should either:

1. Auto-compact before hitting the 20MB limit, or
2. At minimum, include a suggestion to run /compact in the error message

Actual behavior: Every subsequent request just fails with the same error, no guidance provided.