uv/tests: add an unresolvable test case involving overlapping markers

This example came up in discussion and it was initially unclear whether
we should try to support it. Specifically, by automatically assuming
that the `datasets < 2.19` dependency had a marker corresponding to the
negation of the conjunction of the other sibling markers for that same
package. But this was deemed, I think, a little too magical.

This in turn implies that whenever there are sibling dependencies with
overlapping marker expressions, their version constraints also need to
be overlapping. Otherwise, for any marker environment that matches both
marker expressions, it would be impossible to select a single version.

crates/uv/tests/lock.rs

@@ -7617,3 +7617,38 @@ fn lock_mismatched_versions() -> Result<()> {
 
     Ok(())
 }
+
+/// This checks that overlapping marker expressions with disjoint
+/// version constraints fails to resolve.
+#[test]
+fn unconditional_overlapping_marker_disjoint_version_constraints() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.11"
+        dependencies = [
+            "datasets < 2.19",
+            "datasets >= 2.19 ; python_version > '3.10'"
+        ]
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `uv lock` is experimental and may change without warning
+      × No solution found when resolving dependencies for split (python_version > '3.10'):
+      ╰─▶ Because only datasets{python_version > '3.10'}<2.19 is available and project==0.1.0 depends on datasets{python_version > '3.10'}>=2.19, we can conclude that project==0.1.0 cannot be used.
+          And because only project==0.1.0 is available and you require project, we can conclude that the requirements are unsatisfiable.
+    "###);
+
+    Ok(())
+}