fix(release): publish v-prefixed GHCR image tags and align Helm appVersion

Closes #136

goreleaser was publishing ghcr.io/dvflw/mantle:0.4.0 (bare version) but not
the v-prefixed form that Kubernetes manifests and Helm charts conventionally
reference. Add a dedicated v{{ .Version }} manifest alongside the existing
bare-version manifest so both resolve.

Helm chart: default image.tag to the chart's appVersion (formatted as
v<version>) when the value is left empty, so chart upgrades automatically
track the correct image. Update Chart.yaml appVersion from 0.1.0 → 0.4.0
to match the current engine release.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people

packages/engine/.goreleaser.yaml

@@ -68,6 +68,12 @@ dockers_v2:
       - "--platform=linux/arm64"
 
 docker_manifests:
+  # v-prefixed tag (e.g. v0.4.0) — the canonical form users and Helm charts reference.
+  - name_template: "ghcr.io/dvflw/mantle:v{{ .Version }}"
+    image_templates:
+      - "ghcr.io/dvflw/mantle:{{ .Version }}-amd64"
+      - "ghcr.io/dvflw/mantle:{{ .Version }}-arm64"
+  # Bare version without v prefix (e.g. 0.4.0) for tooling that strips it.
   - name_template: "ghcr.io/dvflw/mantle:{{ .Version }}"
     image_templates:
       - "ghcr.io/dvflw/mantle:{{ .Version }}-amd64"

packages/helm-chart/Chart.yaml

@@ -3,4 +3,4 @@ name: mantle
 description: Headless AI workflow automation platform
 type: application
 version: 0.1.0
-appVersion: "0.1.0"
+appVersion: "0.4.0"

packages/helm-chart/templates/deployment.yaml

@@ -38,7 +38,7 @@ spec:
       terminationGracePeriodSeconds: 40
       containers:
         - name: mantle
-          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
+          image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default (printf "v%s" .Chart.AppVersion) }}"
           imagePullPolicy: {{ .Values.image.pullPolicy }}
           {{- with .Values.securityContext }}
           securityContext:

packages/helm-chart/values.yaml

@@ -2,7 +2,9 @@ replicaCount: 1
 
 image:
   repository: ghcr.io/dvflw/mantle
-  tag: latest
+  # tag defaults to the chart's appVersion (e.g. v0.4.0) when left empty.
+  # Override to pin a specific release: --set image.tag=v0.5.0
+  tag: ""
   pullPolicy: IfNotPresent
 
 database: