Mk `test_crash_handler_cms` suite go green

Turns out there were some subtle internal bugs discovered by the just
added `tests/devx/test_tooling::test_crash_handler_cms` suite.

So this fixes,

- a mis-ordering around `rt_repl_fixture :=` in the logic of
  `DebugStatus.maybe_enter_repl_fixture()`.

- `.devx.debug._post_mortem._post_mortem()` ensuring we now **always**
  call `DebugStatus.release()`, and thus unwind the exist-stack managing
  the `repl_fixture` exit/teardown, **even in the case** where
  `yield False` is delivered from the user-fixture-fn (meaning
  `dnter_repl=False`) thus triggering an early `return` (as is done in
  the new test suite).

tractor/devx/debug/_post_mortem.py

@@ -148,7 +148,9 @@ def _post_mortem(
         repl_fixture=repl_fixture,
         boxed_maybe_exc=boxed_maybe_exc,
     )
+    try:
         if not enter_repl:
+            # XXX, trigger `.release()` below immediately!
             return
         try:
             actor: Actor = current_actor()
@@ -194,7 +196,7 @@ def _post_mortem(
             # frame=None,
             traceback=tb,
         )
-
+    finally:
         # XXX NOTE XXX: this is abs required to avoid hangs!
         #
         # Since we presume the post-mortem was enaged to

tractor/devx/debug/_tty_lock.py

@@ -846,9 +846,9 @@ class DebugStatus:
 
         '''
         if not (
-            repl_fixture
-            or
             (rt_repl_fixture := _state._runtime_vars.get('repl_fixture'))
+            or
+            repl_fixture
         ):
             return True  # YES always enter