feat: remove legacy OpenCode runtime

Cut product flows over to Coding/Pi and retain only the migration-owned v1 boundary. Promote supported native optional packages because electron-builder omitted pnpm transitive optional closure from the packaged ASAR.

scripts/after-pack.cjs

@@ -55,6 +55,7 @@ const PERSISTED_USER_DATA_FILES = new Set([
   'gateway-prelaunch-maintenance-cache.json',
   'niancode-device-identity.json',
   'niancode-providers.json',
+  // Legacy installed-user store filename; it must never enter an artifact.
   'opencode-projects.json',
   'settings.json',
 ]);