This PR:
- centralizes filesystem path construction for API-provided slugs and
filenames in `composio.utils.safe_path`
- rejects traversal, Windows-invalid names, invalid Unicode, and
overlong encoded filenames before creating directories or writing files
- normalizes trusted roots consistently and routes both Python download
paths through the shared helpers
- adds a fail-closed AST guard for new dynamic path construction,
including direct `Path(...)` calls
- isolates provider initialization from the real home directory and
makes the home-write guard report changes without deleting them
- removes the obsolete download filename wrapper
## Verification
- `pytest -q`: 1,248 passed, 47 skipped
- repository-configured Ruff checks and formatting passed for every
changed Python file
- targeted mypy checks passed for the changed helpers and tests
Alberto Schiabel