test(issue-28): make the host-dependent tests portable; POSIX ps in the process scanners

The 33 failures on the Linux / Python 3.14 host (#28) were environment
dependencies, not regressions; each test is worth keeping, so fix the
dependency instead of deleting the test:

- test_workspace_scope: `source` under `shell=True` ran in dash; run the
  command string under bash.
- conftest autouse: MAM_ENV_FILE points at an absent file for every test,
  so a workspace .mam.env with a reachable broker no longer breaks the
  "broker unavailable" tests (T1-4).
- help-capture guard: compare normalized help text (whitespace collapsed,
  "optional arguments"/"options" unified) so argparse re-wrapping across
  Python versions is not drift.
- deploy freshness D-11..D-19 and D-22..D-30: skip with a reason when the
  nats-docker submodule is not initialized.
- lib_py.agents.base.conversation_in_use and heartbeat._process_table:
  `ps -eo pid=,ppid=,args=` (POSIX) instead of the BSD `-axo ... command=`
  form, the most likely cause of the 12 purge failures on Linux (the holder
  scan returned nothing); to be confirmed on that host.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

tests/conftest.py

@@ -170,6 +170,11 @@ def _isolate_mam_state_dirs(_ambient_control_plane, tmp_path, monkeypatch):
     state = tmp_path / ".mam-test-state"
     monkeypatch.setenv("MAM_JOBS_DIR", str(state / "jobs"))
     monkeypatch.setenv("DELEGATE_JOB_LOGS_DIR", str(state / "delegate_job_logs"))
+    # Issue #28: a workspace whose real .mam.env names a reachable broker made
+    # "broker unavailable" tests (T1-4) read it through the wrapper's env loader.
+    # Point every test at an absent env file; a test that wants a real broker
+    # config sets MAM_ENV_FILE itself.
+    monkeypatch.setenv("MAM_ENV_FILE", str(state / ".mam.env.absent"))
 
 
 @pytest.fixture