fix(mypy): add type stubs and fix typing issues (#3938)

Adds type stubs and fixes mypy errors for better type coverage.

Changes:
- Added type_checking dependency group with type stubs (torchtune, trl,
etc.)
- Added lm-format-enforcer to pre-commit hook
- Created HFAutoModel Protocol for type-safe HuggingFace model handling
- Added mypy.overrides for untyped libraries (torchtune, fairscale,
etc.)
- Fixed type issues in post-training providers, databricks, and
api_recorder

Note: ~1,200 errors remain in excluded files (see pyproject.toml exclude
list).

---------

Co-authored-by: Claude <noreply@anthropic.com>

.pre-commit-config.yaml

@@ -57,18 +57,17 @@ repos:
     hooks:
     -   id: uv-lock
 
--   repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.16.1
+-   repo: local
     hooks:
     -   id: mypy
+        name: mypy
         additional_dependencies:
-          - uv==0.6.2
-          - mypy
-          - pytest
-          - rich
-          - types-requests
-          - pydantic
+          - uv==0.7.8
+        entry: uv run --group dev --group type_checking mypy
+        language: python
+        types: [python]
         pass_filenames: false
+        require_serial: true
 
 # - repo: https://github.com/tcort/markdown-link-check
 #   rev: v3.11.2