chore: draft unreleased changelog, bump opencode sdk to 1.17.18

Changelog leads with the private relay and the native mobile apps (TestFlight
beta + Android APK links), followed by pairing v2 and the device management,
desktop multi-transport, and chat items; VS Code changelog gets the shared
chat-render entries.

packages/ui/package.json

@@ -43,7 +43,7 @@
     "@dnd-kit/sortable": "^10.0.0",
     "@dnd-kit/utilities": "^3.2.2",
     "@lezer/highlight": "^1.2.3",
-    "@opencode-ai/sdk": "1.17.12",
+    "@opencode-ai/sdk": "1.17.18",
     "@pierre/diffs": "1.3.0-beta.6",
     "@replit/codemirror-vim": "^6.3.0",
     "@simplewebauthn/browser": "13.3.0",