feat: Tools multi-version selector helpers

[mallardduck]

Attempt to solve: #29

• Adjusts helmv4 to be default helm binary (leaves helm_v3 alias used in some CIs for helm 3)
• Adds concept of "tool family" to group tools and generate selector helper scripts
• Adds new tool family concept to relevant lock file generation
• Add /var/ci-tools/active to PATH to ensure selected tools come first

DEMO:

Change helm with helm specific helper:

→ docker run -it ghcr.io/rancher/ci-image/go1.25:latest
7a4f7716c530:/go # helm version
version.BuildInfo{Version:"v4.1.4", GitCommit:"05fa37973dc9e42b76e1d2883494c87174b6074f", GitTreeState:"clean", GoVersion:"go1.25.9", KubeClientVersion:"v1.35"}
7a4f7716c530:/go # select-helm helmv3
helm is now: helmv3
7a4f7716c530:/go # helm version
version.BuildInfo{Version:"v3.20.2", GitCommit:"8fb76d6ab555577e98e23b7500009537a471feee", GitTreeState:"clean", GoVersion:"go1.25.9"}

Or with core helper (which all tool-family specific ones use):

7a4f7716c530:/go # ci-select helm helmv4
helm is now: helmv4
7a4f7716c530:/go # helm version
version.BuildInfo{Version:"v4.1.4", GitCommit:"05fa37973dc9e42b76e1d2883494c87174b6074f", GitTreeState:"clean", GoVersion:"go1.25.9", KubeClientVersion:"v1.35"}

[mallardduck]

Long term @macedogm plan to get packages installable via zypper to enable multiple version support is best. However this will enable devs to solve the DX issue with multiple binary tools immediately.

[Copilot]

Pull request overview

Adds “tool family” selectors to Rancher CI images so multiple versions of a tool (e.g., Helm v3/v4) can coexist and be switched at runtime via ci-select / select-<family> helpers, addressing #29.

Changes:

• Introduces selector infrastructure (manifest + active symlinks) and prepends /var/ci-tools/active to PATH for images that include selectors.
• Adds generator support for per-family and generic selector scripts, and records selectors in images-lock.yaml + changelog diffing.
• Renames Helm v3 binary to helmv3 and makes Helm v4 the default helm via the selector.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
internal/dockerfile/tmpl/selector_setup.tmpl	Adds template to create selector manifest + default active symlinks during image build.
internal/dockerfile/tmpl/dockerfile.tmpl	Wires selector setup into rendered Dockerfiles (PATH, COPY scripts, RUN setup).
internal/dockerfile/spec.go	Adds selector metadata to DockerfileVars and template-rendered setup command helper.
internal/dockerfile/generate.go	Generates ci-select.sh and per-family select-*.sh scripts; provides selector-family name listing.
internal/dockerfile/build.go	Collects selector families/defaults per image and passes them into Dockerfile rendering.
internal/config/validate.go	Validates family definitions and blocks alias names that would conflict with selectors.
internal/config/config.go	Extends tool schema with family + family_default; introduces ChecksumList type alias.
internal/cli/generate.go	Writes selector scripts to dockerfiles/scripts/ and cleans up stale selector scripts; extends images-lock structure.
internal/changelog/types.go	Extends lock/changelog types to include selectors and per-image selector default changes.
internal/changelog/diff_test.go	Adds tests for selector added/removed/default-changed diff behavior.
internal/changelog/diff.go	Computes selector diffs globally and selector-default changes per image.
internal/changelog/changelog.go	Renders selector additions/removals and per-image default changes in changelog entries.
images-lock.yaml	Records selector families and per-image family defaults; renames helm tool entry to helmv3.
dockerfiles/scripts/select-helm.sh	Adds helm-specific wrapper script invoking ci-select helm.
dockerfiles/scripts/ci-select.sh	Adds generic selector script to list/select tools by family using the manifest.
dockerfiles/Dockerfile.python3.13	Applies selector PATH + scripts; renames helm v3 install to helmv3; sets up helm family selector.
dockerfiles/Dockerfile.python3.11	Applies selector PATH + scripts; renames helm v3 install to helmv3; sets up helm family selector.
dockerfiles/Dockerfile.node24	Applies selector PATH + scripts; renames helm v3 install to helmv3; sets up helm family selector.
dockerfiles/Dockerfile.node22	Applies selector PATH + scripts; renames helm v3 install to helmv3; sets up helm family selector.
dockerfiles/Dockerfile.go1.26	Applies selector PATH + scripts; renames helm v3 install to helmv3; updates helm_v3 alias; sets up selector.
dockerfiles/Dockerfile.go1.25	Applies selector PATH + scripts; renames helm v3 install to helmv3; updates helm_v3 alias; sets up selector.
dockerfiles/Dockerfile.charts	Applies selector PATH + scripts; renames helm v3 install to helmv3; sets up helm family selector.
deps.yaml	Renames helm v3 tool to helmv3, defines helm family and default (helmv4), updates helm_v3 alias targets.

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