Fix wrap() to use scheme_from_name instead of scheme_from_content

PixiBuilder.wrap() and UvBuilder.wrap() were calling scheme_from_content()
with a filename string (e.g. "pixi.toml") instead of file content. Since
RequirementsTxtScheme.supports_content() matches any bare word, this caused
every wrapped environment's scheme to be misdetected as "requirements.txt".
The bug was latent before, but was exposed by the early scheme validation
added in the previous content-validation commit.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ctrueden

src/appose/builder/pixi.py

@@ -12,7 +12,7 @@
 
 from . import BaseBuilder, BuildException, Builder, BuilderFactory
 from ..environment import Environment
-from ..scheme import from_content as scheme_from_content
+from ..scheme import from_content as scheme_from_content, from_name as scheme_from_name
 from ..tool.pixi import Pixi
 
 
@@ -250,15 +250,15 @@ def wrap(self, env_dir: str | Path) -> Environment:
             # Read the content so rebuild() will work even after directory is deleted
             with open(pixi_toml, "r", encoding="utf-8") as f:
                 self._content = f.read()
-            self._scheme = scheme_from_content("pixi.toml")
+            self._scheme = scheme_from_name("pixi.toml")
         else:
             # Check for pyproject.toml
             pyproject_toml = env_path / "pyproject.toml"
             if pyproject_toml.exists() and pyproject_toml.is_file():
                 # Read the content so rebuild() will work even after directory is deleted
                 with open(pyproject_toml, "r", encoding="utf-8") as f:
                     self._content = f.read()
-                self._scheme = scheme_from_content("pyproject.toml")
+                self._scheme = scheme_from_name("pyproject.toml")
 
         # Set the base directory and build (which will detect existing env)
         self.base(env_path)

src/appose/builder/uv.py

@@ -12,7 +12,7 @@
 
 from . import BaseBuilder, BuildException, Builder, BuilderFactory
 from ..environment import Environment
-from ..scheme import from_content as scheme_from_content
+from ..scheme import from_content as scheme_from_content, from_name as scheme_from_name
 from ..tool.uv import Uv
 from ..util.platform import is_windows
 
@@ -195,15 +195,15 @@ def wrap(self, env_dir: str | Path) -> Environment:
             # Read the content so rebuild() will work even after directory is deleted
             with open(pyproject_toml, "r", encoding="utf-8") as f:
                 self._content = f.read()
-            self._scheme = scheme_from_content("pyproject.toml")
+            self._scheme = scheme_from_name("pyproject.toml")
         else:
             # Fall back to requirements.txt
             requirements_txt = env_path / "requirements.txt"
             if requirements_txt.exists() and requirements_txt.is_file():
                 # Read the content so rebuild() will work even after directory is deleted
                 with open(requirements_txt, "r", encoding="utf-8") as f:
                     self._content = f.read()
-                self._scheme = scheme_from_content("requirements.txt")
+                self._scheme = scheme_from_name("requirements.txt")
 
         # Set the base directory and build (which will detect existing env)
         self.base(env_path)