feat: add IDE choice — VSCode (default), Google Antigravity, SSH

- Add `ide` Helm value with options: vscode, antigravity, ssh
- Dockerfile: install Google Antigravity via apt and openssh-server
- scripts/startapp.sh: branch on IDE env var to launch the right app
- scripts/cont-init-sshd.sh: start sshd as root in SSH mode, set up
  authorized_keys from SSH_AUTHORIZED_KEYS env var
- chart/templates/deployment.yaml: pass IDE env var, conditional ports
  and probes (HTTP for VNC modes, TCP socket for SSH mode)
- chart/templates/service.yaml: expose port 5800 (VNC) or 22 (SSH)
- chart/values.yaml: add ide field with documentation
- README.md: document IDE choice, fix stale happyHomeDir references
- chart/Chart.yaml: bump to 0.1.5

Closes #10

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

scripts/startapp.sh

@@ -14,8 +14,21 @@ else
     WORKSPACE_DIR="/workspace/default"
 fi
 
-echo "Opening Antigravity in: $WORKSPACE_DIR"
+IDE="${IDE:-vscode}"
+echo "IDE mode: $IDE"
+echo "Workspace: $WORKSPACE_DIR"
 
-# Start Antigravity (VSCode) in the workspace directory as claude user
-# The baseimage-gui will handle the GUI display
-exec code --new-window --wait "$WORKSPACE_DIR"
+case "$IDE" in
+    antigravity)
+        echo "Opening Google Antigravity in: $WORKSPACE_DIR"
+        exec antigravity --new-window --wait "$WORKSPACE_DIR"
+        ;;
+    ssh)
+        echo "SSH mode: sshd started by cont-init. Keeping container alive."
+        exec sleep infinity
+        ;;
+    *)
+        echo "Opening VSCode in: $WORKSPACE_DIR"
+        exec code --new-window --wait "$WORKSPACE_DIR"
+        ;;
+esac