refactor: make SSH additive boolean, add ide=none

SSH is now a standalone `ssh: true/false` value that starts sshd on
port 22 *in addition to* whatever IDE is running, rather than replacing
it. The `ide` value loses the `ssh` option and gains `none` (keep
container alive with no GUI IDE, useful when ssh: true is the only
access method).

- chart/values.yaml: replace `ide: ssh` with `ssh: false` boolean
- chart/templates/deployment.yaml: expose port 22 when ssh=true,
  port 5800 when ide!=none; probes use HTTP (VNC) or TCP socket (SSH-only)
- chart/templates/service.yaml: include both ports when both enabled
- scripts/cont-init-sshd.sh: check SSH=true instead of IDE=ssh
- scripts/startapp.sh: add ide=none case (sleep infinity), drop ssh case
- chart/Chart.yaml: bump to 0.1.6
- README.md: update IDE choice and SSH access docs

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

chart/templates/service.yaml

@@ -6,16 +6,17 @@ metadata:
     {{- include "antigravity.labels" . | nindent 4 }}
 spec:
   ports:
-    {{- if eq (.Values.ide | default "vscode") "ssh" }}
-    - port: 22
-      name: ssh
-      protocol: TCP
-      targetPort: ssh
-    {{- else }}
+    {{- if ne (.Values.ide | default "vscode") "none" }}
     - port: 5800
       name: vnc-web
       protocol: TCP
       targetPort: vnc-web
     {{- end }}
+    {{- if .Values.ssh }}
+    - port: 22
+      name: ssh
+      protocol: TCP
+      targetPort: ssh
+    {{- end }}
   selector:
     {{- include "antigravity.labels" . | nindent 4 }}