deps: pin sifter-build by tag 2.0.0; drop dev-env exclude-newer from lock

Pin to the 2.0.0 release tag rather than a commit SHA, and regenerate
uv.lock with UV_EXCLUDE_NEWER unset so it carries no relative
exclude-newer span (which made `uv sync --locked` fail in CI).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: danl-aisi

pyproject.toml

@@ -40,7 +40,7 @@
 [tool.uv]
     environments=["sys_platform == 'linux'"]
     [tool.uv.sources]
-        sifter-build=[{git="https://github.com/UKGovernmentBEIS/sifter-build.git", rev="8d48ef78d448d8780999debdfc286c43afa71214"}]
+        sifter-build=[{git="https://github.com/UKGovernmentBEIS/sifter-build.git", tag="2.0.0"}]
         torch=[{index="pytorch-cu126", marker="sys_platform == 'linux'"}]
 
 [dependency-groups]