chore(release): 0.4.8 (versionCode 35) — ship retention improvements (#112)

Bundles the unreleased work sitting on main since v0.4.7:
- Offline demo mode (#108) — value without a server
- First-run clarity + fast-fail connect timeout (#107)
- Directory-browser stuck-state fix (#106)

Version + versionCode bumped and a user-facing changelog added so the owner
can cut the release (tag v0.4.8 / dispatch publish-play-store.yml). Does NOT
itself publish — releasing to production stays an owner action.


Claude-Session: https://claude.ai/code/session_01T12AhSnQVrSxNnvwfCx2z6

Co-authored-by: engineer <engineer@macbookpro.lan>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

app.json

@@ -2,7 +2,7 @@
   "expo": {
     "name": "OpenCode",
     "slug": "opencode-mobile",
-    "version": "0.4.7",
+    "version": "0.4.8",
     "orientation": "portrait",
     "scheme": "opencode",
     "userInterfaceStyle": "automatic",
@@ -35,7 +35,7 @@
     },
     "android": {
       "package": "cc.agentlabs.opencode",
-      "versionCode": 34,
+      "versionCode": 35,
       "usesCleartextTraffic": true,
       "adaptiveIcon": {
         "foregroundImage": "./assets/adaptive-icon.png",