fix: mount memory-backed emptyDir at /dev/shm for Electron apps

Instead of disabling shared memory usage, mount a proper tmpfs at
/dev/shm so Antigravity (and Chrome) have real shared memory available.
Removes --disable-dev-shm-usage; keeps --no-sandbox (separate issue).

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

chart/Chart.yaml

@@ -2,5 +2,5 @@ apiVersion: v2
 name: devcontainer
 description: Antigravity Dev Container with Happy Coder AI assistant
 type: application
-version: 0.1.8
+version: 0.1.9
 appVersion: "latest"