Migrate filesystem operations to use the io.Local abstraction for
improved security, testability, and consistency:
- pkg/cache: Replace os.ReadFile, WriteFile, Remove, RemoveAll with
io.Local equivalents. io.Local.Write creates parent dirs automatically.
- pkg/agentic: Migrate config.go and context.go to use io.Local for
reading config files and gathering file context.
- pkg/repos: Use io.Local.Read, Exists, IsDir, List for registry
operations and git repo detection.
- pkg/release: Use io.Local for config loading, existence checks,
and artifact discovery.
- pkg/devops/sources: Use io.Local.EnsureDir for CDN download.
All paths are converted to absolute using filepath.Abs() before
calling io.Local methods to handle relative paths correctly.
Closes#104, closes#106, closes#108, closes#111
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>