docs: comprehensive documentation update for Helm chart and MCP sidecars

- Added MCP sidecar configuration documentation across all docs
- Migrated from kustomize to Helm-based deployment instructions
- Updated Makefile with new helm-* targets, removed outdated k8s-* targets
- Rewrote DEPLOYMENT.md to focus on Helm chart deployment
- Transformed VARIABLES.md into complete Helm values reference
- Added MCP sidecar section to README.md with configuration examples

Key improvements:
- Clear instructions for enabling/disabling MCP servers
- Consistent Helm-based deployment throughout documentation
- Comprehensive values reference with examples
- Better organization for different deployment scenarios

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

README.md

@@ -150,6 +150,54 @@ helm install mydev ./chart \
 
 With any non-`none` value, a `ServiceAccount` named `devcontainer-{name}` is created and set as the pod's `serviceAccountName`, so `kubectl` and any in-cluster API calls use it automatically.
 
+### MCP Sidecars
+
+The devcontainer includes MCP (Model Context Protocol) servers as sidecar containers that enable AI assistants to interact with Kubernetes and Flux:
+
+| Sidecar | Default | Purpose |
+|---------|---------|---------|
+| `mcpSidecars.kubernetes.enabled` | `true` | Kubernetes API access via MCP |
+| `mcpSidecars.flux.enabled` | `true` | Flux GitOps operations via MCP |
+
+These sidecars inherit the pod's ServiceAccount RBAC permissions (controlled by `clusterAccess`).
+
+**Disable MCP sidecars:**
+```bash
+# Disable both sidecars
+helm install mydev ./chart \
+  --set name=mydev \
+  --set githubRepo=https://github.com/youruser/yourrepo \
+  --set mcpSidecars.kubernetes.enabled=false \
+  --set mcpSidecars.flux.enabled=false
+
+# Or selectively disable
+helm install mydev ./chart \
+  --set name=mydev \
+  --set githubRepo=https://github.com/youruser/yourrepo \
+  --set mcpSidecars.flux.enabled=false  # Disable only Flux MCP
+```
+
+**Custom MCP configuration:**
+```yaml
+# values.yaml override
+mcpSidecars:
+  kubernetes:
+    enabled: true
+    image:
+      repository: quay.io/containers/kubernetes_mcp_server
+      tag: latest
+    port: 8080
+    resources:
+      requests:
+        memory: "64Mi"
+        cpu: "50m"
+      limits:
+        memory: "256Mi"
+        cpu: "500m"
+  flux:
+    enabled: false  # Disabled in this example
+```
+
 ### Display and resources
 
 | Value | Default | Description |