Use //go:fix inline for deprecated storage backends and migrate off deprecated pipeline APIs

Description

Go 1.26 introduced //go:fix inline — a directive that allows go fix and IDEs to automatically rewrite call sites of deprecated functions, type aliases, and variables to their modern replacements. See the Go blog post for details.

There are two sides to this for tektoncd/chains:

1. As a consumer: Once tektoncd/pipeline adds //go:fix inline annotations to its deprecated APIs, chains can run go fix ./... to auto-migrate (e.g. v1beta1 type aliases, deprecated resolution APIs).

2. As a library: chains has its own deprecated types that could benefit from annotation.

Prerequisite

Bump go.mod to Go 1.26 (currently at 1.25.5).

Opportunities

Deprecated Storage Backends

The following storage backends are deprecated in favor of Storer:

• pkg/chains/storage/tekton/tekton.go — Backend struct (deprecated, use Storer instead)
• pkg/chains/storage/gcs/gcs.go — Backend struct
• pkg/chains/storage/oci/legacy.go — Backend struct

If there are constructor functions like NewStorageBackend() that simply wrap the new API, those can be annotated with //go:fix inline:

// Deprecated: use NewStorer instead.
//
//go:fix inline
func NewStorageBackend(ps versioned.Interface) *Backend {
	return &Backend{pipelineclientset: ps}
}

Consuming pipeline's annotations

Once tektoncd/pipeline annotates its deprecated APIs (tektoncd/pipeline#9560), running go fix ./... in chains will automatically migrate:

• v1beta1.ArrayOrString → v1beta1.ParamValue
• Deprecated resolution package imports
• Other deprecated type aliases and wrapper functions

References

• //go:fix inline and the source-level inliner
• Using go fix to modernize Go code
• Related: tektoncd/pipeline#9560

Start with go.mod and the deprecated Backend definitions in pkg/chains/storage/tekton/tekton.go, pkg/chains/storage/gcs/gcs.go, and pkg/chains/storage/oci/legacy.go. Check tektoncd/pipeline#9560 before running go fix ./... to identify migrations enabled by the dependency. Done means Go 1.26 is required and the applicable deprecated storage APIs and pipeline usages are migrated or annotated.