fix(deps): update ML dependencies for smolagents compatibility

smolagents>=1.0.0 requires huggingface-hub>=0.31.2, but we had
huggingface_hub==0.20.3 pinned. Update all ML dependencies to
compatible versions:

- huggingface_hub: 0.20.3 → >=0.31.2
- transformers: 4.37.2 → >=4.40.0
- accelerate: 0.26.1 → >=0.30.0
- bitsandbytes: 0.42.0 → >=0.42.0
- torch: 2.2.0 → >=2.2.0

Also update constraints.txt to match.

Author: Sakeeb91

constraints.txt

@@ -1,16 +1,15 @@
 #
-# Pinned lower bounds to avoid pip "resolution-too-deep" errors in CI.
-# Keep in sync with requirements.txt when adjusting core dependencies.
+# Constraints file for dependency resolution.
+# Now using uv which handles resolution efficiently.
+# Keep in sync with requirements.txt.
 #
 cryptography>=39.0.0
 numpy<2
-# Pin smolagents to avoid resolution issues
 smolagents>=1.0.0,<2.0.0
-# Pin coverage to avoid backtracking through versions
 coverage>=7.4.0
-# Pin other common backtracking dependencies
-huggingface_hub>=0.20.0
-transformers>=4.37.0
+huggingface_hub>=0.31.2
+transformers>=4.40.0
+accelerate>=0.30.0
 fsspec>=2023.5.0
 tokenizers>=0.15.0
 

requirements.txt

@@ -5,12 +5,12 @@ pydantic==2.6.1
 pydantic-settings==2.1.0
 
 # ML & NLP
-transformers==4.37.2
-torch==2.2.0
-accelerate==0.26.1
-huggingface_hub==0.20.3
-bitsandbytes==0.42.0
-numpy<2  # Required for torch 2.2.0 compatibility
+transformers>=4.40.0
+torch>=2.2.0
+accelerate>=0.30.0
+huggingface_hub>=0.31.2
+bitsandbytes>=0.42.0
+numpy<2  # Required for torch compatibility
 
 # Agent Framework (Issue #18: smolagents integration)
 smolagents>=1.0.0