feat: add multi-repo cloning, remove dynamic/serverless mode

Add githubRepos list field for cloning multiple repositories into a
single dev container with multi-root workspace file generation.
Remove the unused dynamic deployment mode (Knative, routing proxy,
serverless scripts) to simplify the chart to persistent-only.
Fix release workflow cache-to setting that violated the no-cache policy.

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

chart/templates/rbac.yaml

@@ -1,4 +1,3 @@
-{{- if eq .Values.deploymentMode "persistent" }}
 {{- $access := .Values.clusterAccess | default "none" }}
 {{- $name   := include "devcontainer.fullname" . }}
 {{- $ns     := .Release.Namespace }}
@@ -96,4 +95,3 @@ roleRef:
 {{- end }}
 
 {{- end }}
-{{- end }}