feat: support helm charts in kustomizations

[vincent-onebrief]

Description

Currently kustomizations with helm chart references fail, even with plugins enabled.

# zarf.yaml
components:
  - name: keycloak-server
    default: true
    manifests:
      - name: keycloak-server
        namespace: keycloak
        kustomizations:
          - .
        enableKustomizePlugins: true

# kustomization.yaml
namespace: keycloak
helmCharts:
  - releaseName: keycloak
    name: keycloak
    repo: oci://registry-1.docker.io/bitnamicharts
    version: "23.3.3"
    valuesFile: values.yaml

$ zarf dev inspect manifests .

2026-02-03 13:54:02 ERR unable to build kustomization .: trouble configuring builtin HelmChartInflationGenerator with config: `
name: keycloak
namespace: keycloak
releaseName: keycloak
repo: oci://registry-1.docker.io/bitnamicharts
valuesFile: values.yaml
version: 26.3.3
`: must specify --enable-helm

This can be worked around with an onCreate action that renders the manifests, but that's kinda jank and breaks zarf dev inspect and zarf dev find-images.

# zarf.yaml
components:
  - name: keycloak-server
    default: true
    actions:
      onCreate:
        before:
          - description: kustomize build
            cmd: kubectl kustomize --enable-helm > generated.yaml
    manifests:
      - name: keycloak-server
        namespace: keycloak
        files:
          - generated.yaml

This PR enables helm inside kustomizations when enableKustomizePlugins is set, and adds tests to validate functionality

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide Steps followed

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[vincent-onebrief]

Added tests fail as expected with build.go changes commented out

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/internal/packager/kustomize/build.go	78.57% <100.00%> (+78.57%)	⬆️

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[a1994sc]

I half wonder if after #4350 is merged we should update this to use zarf tools helm.

Not a blocker, but a potential follow-up pr.

[AustinAbro321]

Yeah, #4350 is close but blocked by a bug in Helm that will be fixed in the next Helm release.

I do think we should block this PR on that, the quasi Helm fork currently in Zarf is outdated, and I would like to avoid relying on the host binary, so that package builds are the same across devices

[AustinAbro321]

Marking this as blocked by #4350 which will fully embed Helm into the Zarf binary and should allow this to be done looking for the host binary