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

.agents/skills/lib_py/agents/base.py

@@ -47,7 +47,7 @@ def conversation_in_use(uuid: str, paths=()) -> bool:
         if os.environ.get(var, "").strip() == uuid:
             return True
     try:
-        out = subprocess.run(["ps", "-axo", "pid=,ppid=,command="],
+        out = subprocess.run(["ps", "-eo", "pid=,ppid=,args="],
                              capture_output=True, text=True, timeout=10).stdout
     except Exception:
         out = ""