test(host_agent): assert parsed agent version matches AGENT_VERSION constant

The on-disk-version test hardcoded '1.0.0' and broke on the 1.1.0 bump. Compare
against agent.AGENT_VERSION so future bumps don't require touching the test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/plugins/host_agent/test_install_template.py

@@ -69,6 +69,9 @@ def test_rendered_script_passes_sh_n(tmp_path):
 
 
 def test_agent_version_parses_on_disk_agent():
+    # Version-agnostic: the parsed value must match the agent module's constant,
+    # so a future AGENT_VERSION bump doesn't require touching this test.
+    from plugins.host_agent import agent
     assert AGENT_SOURCE_PATH.exists()
     v = _agent_version()
-    assert v == "1.0.0"
+    assert v == agent.AGENT_VERSION