Only include specifically-requested packages in radioconda metapackage.

Including the fully solved list of packages is fragile to packages
getting marked broken or having their metadata rewritten, making the
radioconda metapackage uninstallable. This doesn't completely solve that
(nothing really can), but it does make the metapackage still fulfill its
intended purpose while hopefully remaining installable more often.

rerender.py

@@ -198,15 +198,6 @@ def render_platforms(
         else:
             variables = None
 
-        # write the full environment specification to a yaml file (to build metapackage)
-        locked_env_dict = write_env_file(
-            env_spec=locked_env_spec,
-            file_path=output_dir / f"{output_name}.yml",
-            name=env_name,
-            version=version,
-            variables=variables,
-        )
-
         # write the full environment specification to a lock file (to install from file)
         lockfile_contents = write_lock_file(
             lock_spec=locked_env_spec,
@@ -214,6 +205,27 @@ def render_platforms(
             conda_exe=conda_exe,
         )
 
+        # filter the full package spec by the explicitly listed package names
+        metapackage_pkg_specs = [
+            spec
+            for spec in locked_env_spec.specs
+            if name_from_pkg_spec(spec) in env_spec.specs
+        ]
+        metapackage_spec = conda_lock.src_parser.LockSpecification(
+            specs=metapackage_pkg_specs,
+            channels=locked_env_spec.channels,
+            platform=locked_env_spec.platform,
+        )
+
+        # write the filtered environment spec to a yaml file (to build metapackage)
+        locked_env_dict = write_env_file(
+            env_spec=metapackage_spec,
+            file_path=output_dir / f"{output_name}.yml",
+            name=env_name,
+            version=version,
+            variables=variables,
+        )
+
         # add installer-only (base environment) packages and lock those too
         installer_pkg_spec = conda_lock.conda_lock.parse_environment_file(
             environment_file=installer_environment_file, platform=platform