Refactor setup workflow and make install robust via virtualenv

- Introduce a dedicated Python virtualenv (deps target) and run all setup scripts through it
- Fix missing PyYAML errors in clean, CI, and Nix environments
- Refactor build defaults into cli/setup for clearer semantics
- Make setup deterministic and independent from system Python
- Replace early Makefile shell expansion with runtime evaluation
- Rename messy-test to test-messy and update deploy logic and tests accordingly
- Keep setup and test targets consistent across Makefile, CLI, and unit tests

https://chatgpt.com/share/693de226-00ac-800f-8cbd-06552b2f283c

tests/unit/cli/deploy/test_dedicated.py

@@ -234,8 +234,8 @@ class TestRunAnsiblePlaybook(unittest.TestCase):
             "Expected 'make messy-build' when skip_build=False",
         )
         self.assertTrue(
-            any(call == ["make", "messy-test"] for call in calls),
-            "Expected 'make messy-test' when skip_tests=False",
+            any(call == ["make", "test-messy"] for call in calls),
+            "Expected 'make test-messy' when skip_tests=False",
         )
         self.assertTrue(
             any(
@@ -330,7 +330,7 @@ class TestRunAnsiblePlaybook(unittest.TestCase):
         # No cleanup, no build, no tests, no inventory validation
         self.assertFalse(any(call == ["make", "clean"] for call in calls))
         self.assertFalse(any(call == ["make", "messy-build"] for call in calls))
-        self.assertFalse(any(call == ["make", "messy-test"] for call in calls))
+        self.assertFalse(any(call == ["make", "test-messy"] for call in calls))
         self.assertFalse(
             any(
                 isinstance(call, list)