fix(ci): smoke guard catches tagless builds; DEBUG import must hit the install; pin more workflow invariants

Review findings on PR #13:
- release-branch-semver gives 0.1.0.devN without tags, so the 0.0 guard
  never fired; check_version() now requires >= 0.2 (unit-tested)
- the APPSKELLINGTON_DEBUG child import could resolve the source tree from
  the cwd and false-pass; it now reports its location and must match
- test_ci_workflow: no continue-on-error, matrix python drives container
  and UV_PYTHON, WIP gate compared whole (mutation-tested)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

scripts/smoke_import.py

@@ -1,21 +1,40 @@
 """Smoke-test an *installed* app_skellington (wheel, sdist or index release).
 
-Run it from outside the source tree, so the installed copy is the one imported:
+Run it from outside the source tree:
 
     cd / && python /path/to/scripts/smoke_import.py [EXPECTED_VERSION]
+
+The script's own directory (scripts/) heads sys.path, so the main import
+can't see the source tree. But the APPSKELLINGTON_DEBUG child process puts
+its cwd first, which is why the cwd must be outside the repo. The child's
+import location is checked too, so a wrong cwd fails instead of passing.
 """
 
 import importlib.metadata
 import os
 import pathlib
+import re
 import subprocess
 import sys
 
+# Any real release is >= 0.2. With no tags reachable (a shallow clone),
+# setuptools_scm's release-branch-semver scheme yields 0.1.0.devN, and other
+# schemes yield 0.0.x.
+MIN_RELEASE = (0, 2)
+
 
 def fail(msg):
     sys.exit("smoke FAILED: " + msg)
 
 
+def check_version(version, expected):
+    major_minor = tuple(int(n) for n in re.match(r"(\d+)\.(\d+)", version).groups())
+    if major_minor < MIN_RELEASE:
+        fail("setuptools_scm found no tags (shallow clone?): %s" % version)
+    if expected is not None and version != expected:
+        fail("expected version %s, got %s" % (expected, version))
+
+
 def main(argv):
     expected = argv[1] if len(argv) > 1 else None
 
@@ -35,19 +54,31 @@ def main(argv):
         SubMenu,
     )
 
-    version = importlib.metadata.version("app_skellington")
-    if version.startswith("0.0"):
-        fail("setuptools_scm found no tags (shallow clone?): %s" % version)
-    if expected is not None and version != expected:
-        fail("expected version %s, got %s" % (expected, version))
+    check_version(importlib.metadata.version("app_skellington"), expected)
 
     # _bootstrap.py takes a different code path when APPSKELLINGTON_DEBUG is set.
     env = dict(os.environ, APPSKELLINGTON_DEBUG="1")
-    proc = subprocess.run([sys.executable, "-c", "import app_skellington"], env=env)
+    proc = subprocess.run(
+        [
+            sys.executable,
+            "-c",
+            "import app_skellington, pathlib;"
+            "print(pathlib.Path(app_skellington.__file__).resolve())",
+        ],
+        env=env,
+        stdout=subprocess.PIPE,
+        universal_newlines=True,
+    )
     if proc.returncode != 0:
         fail("import failed with APPSKELLINGTON_DEBUG=1")
+    child_location = proc.stdout.strip().splitlines()[-1]
+    if child_location != str(location):
+        fail(
+            "APPSKELLINGTON_DEBUG import resolved %s, not the installed %s"
+            " (run from outside the source tree)" % (child_location, location)
+        )
 
-    print("smoke ok:", version, location)
+    print("smoke ok:", importlib.metadata.version("app_skellington"), location)
 
 
 if __name__ == "__main__":