refactor: drop decnet- prefix — BEHAVE is now standalone

Rename packages and imports:
  decnet-behave-core  → behave-core
  decnet-behave-shell → behave-shell
  decnet-behave-text  → behave-text
  decnet_behave_*     → behave_*

BEHAVE is no longer a DECNET sub-project.

core/pyproject.toml

@@ -3,7 +3,7 @@ requires = ["setuptools>=68", "wheel"]
 build-backend = "setuptools.build_meta"
 
 [project]
-name = "decnet-behave-core"
+name = "behave-core"
 version = "0.1.0"
 description = "BEHAVE shared observation envelope — schema contract used by BEHAVE-SHELL and BEHAVE-TEXT"
 requires-python = ">=3.11"
@@ -18,7 +18,7 @@ dev = ["pytest>=8", "pytest-cov", "ruff"]
 "Source" = "https://git.resacachile.cl/anti/BEHAVE"
 
 [tool.setuptools.packages.find]
-include = ["decnet_behave_core*"]
+include = ["behave_core*"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]