deps: depend on sifter-build instead of sifter

sifter was re-homed to UKGovernmentBEIS/sifter-build (distribution renamed to
sifter-build; the import name `sifter` is unchanged). Point the dependency and
uv source at the new repo, pinned to its initial commit.

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

Author: danl-aisi

pyproject.toml

@@ -3,7 +3,7 @@
         "python-dotenv==1.2.2",
         "pyyaml==6.0.3",
         "rich==15.0.0",
-        "sifter==2.0.0",
+        "sifter-build==2.0.0",
         "typer==0.26.7",
     ]
     description="Isambard HPC container management utilities"
@@ -40,7 +40,7 @@
 [tool.uv]
     environments=["sys_platform == 'linux'"]
     [tool.uv.sources]
-        sifter=[{git="https://github.com/UKGovernmentBEIS/sifter.git"}]
+        sifter-build=[{git="https://github.com/UKGovernmentBEIS/sifter-build.git", rev="8d48ef78d448d8780999debdfc286c43afa71214"}]
         torch=[{index="pytorch-cu126", marker="sys_platform == 'linux'"}]
 
 [dependency-groups]