perf(pytest): 194s → 4s collection — lazy heavy imports + norecursedirs

Four-part fix for the collection bottleneck that was blocking the dev loop:

1. Lazy mitreattack.stix20 import in attack_stix.py — deferred to first
   _load() call (TYPE_CHECKING guard at top level)

2. Lazy misp_stix_converter import in both MISP export routers — moved
   from module level into the route handler body

3. Lazy attack_catalog / attack_stix in ttp.py repo mixin — thin wrapper
   functions so the import chain never fires at module load time

4. tests/api/conftest.py — `from decnet.web.api import app` moved inside
   the `client()` fixture; `pytest_ignore_collect` broadened to skip all
   test_schemathesis*.py variants (not just test_schemathesis.py), which
   were launching a subprocess server at module-import time

5. pyproject.toml — `norecursedirs` for tests/live, tests/stress,
   tests/service_testing, tests/docker, tests/perf so these directories
   are never entered; `-m` filter removed from addopts (now redundant);
   `--dist loadscope` → `--dist load` to unblock workers immediately

6. behave_core / behave_shell rename — BEHAVE packages dropped the
   `decnet_` prefix; reinstalled editable installs and updated all 14
   import sites across profiler, ttp, bus, and correlation modules

decnet/bus/topics.py

@@ -427,7 +427,7 @@ def attacker_observation(primitive: str) -> str:
     ``cognitive.feedback_loop_engagement``,
     ``motor.shell_mastery.tab_completion``).  Dotted primitives are
     permitted — this matches the format
-    ``decnet_behave_shell.spec.event_adapter.event_topic_for`` produces
+    ``behave_shell.spec.event_adapter.event_topic_for`` produces
     upstream, and DECNET's bus admits the dotted leaf the same way
     :func:`attacker` does for ``session.started``.