* chore(io): migrate pkg/container to Medium abstraction
Migrated State, Templates, and LinuxKitManager in pkg/container to use
the io.Medium abstraction for storage operations.
- Introduced TemplateManager struct to handle template logic with injected medium.
- Updated State struct to use injected medium for persistence.
- Updated LinuxKitManager to hold and use an io.Medium instance.
- Updated all internal callers in internal/cmd/vm and pkg/devops to use new APIs.
- Adapted and maintained comprehensive test coverage in linuxkit_test.go.
- Fixed naming collision with standard io package by aliasing it as goio.
* chore(io): migrate pkg/container to Medium abstraction (v2)
- Migrated State, Templates, and LinuxKitManager in pkg/container to use io.Medium.
- Introduced TemplateManager struct for dependency injection.
- Updated all call sites in internal/cmd/vm and pkg/devops.
- Restored and adapted comprehensive test suite in linuxkit_test.go.
- Fixed naming collisions and followed project test naming conventions.
* chore(io): address PR feedback for container Medium migration
- Added Open method to io.Medium interface to support log streaming.
- Implemented Open in local.Medium and MockMedium.
- Fixed extension inconsistency in GetTemplate (.yml vs .yaml).
- Refactored TemplateManager to use configurable WorkingDir and HomeDir.
- Reused TemplateManager instance in cmd_templates.go.
- Updated LinuxKitManager to use medium.Open for log access.
- Maintained and updated all tests to verify these improvements.
