Fix flaky test tests/support_agent/test_support_console_reader.py::test_sixteen_concurrent_turns_across_orgs_never_cross

The merge lane saw `tests/support_agent/test_support_console_reader.py::test_sixteen_concurrent_turns_across_orgs_never_cross` fail and then pass on a rerun of the same tree. - Test: `tests/support_agent/test_support_console_reader.py::test_sixteen_concurrent_turns_across_orgs_never_cross` - Tree: `dac3b61c3b36d11d8967306bcc3946e6faebb61f` - Lane task: 12151 - Flake record: 01a196de-44ef-7efb-af86-94b453020d74 Make it deterministic; do not delete it unless it tests nothing.

Fixed root cause: shared_module.load handed concurrent first callers a half-executed module (redact_text missing). Loads now locked, deterministic regression test added; quick gate green; PR #7568 queued to merge lane.