fix(tests): u1e gives the wrapper its own WORKSPACE_ROOT - it wrote the checkout's .mam/shim/herdr

test_u1e_a_dry_run_record_is_not_an_open_job (PR #56) ran the delegate-job
wrapper without WORKSPACE_ROOT; the wrapper sources lib.sh, which then
defaults it to the checkout and rewrites <checkout>/.mam/shim/herdr
(found by review 38a64423). The node joins W1's list, which runs its
nodes in a copy of the checkout and fails on any .mam written there.
A scan of the #50/#55 and leak modules from a clean worktree found no
other writer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

tests/test_issue17_workspace_root_isolation.py

@@ -40,6 +40,7 @@ NODES = [
     "tests/test_issue17_item4_decisions.py::test_c_cmd_wait",
     "tests/test_o2_race_free_lock.py::test_o2_12_run_loop_exits_on_lock_failure",
     "tests/test_o1_rebuttal.py::test_v3_rebut_option_parsing_and_budget",
+    "tests/test_issue50_dispatch.py::test_u1e_a_dry_run_record_is_not_an_open_job",
 ]