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.

electron-builder.yml

@@ -25,9 +25,6 @@ extraResources:
       - "!bin/**"
       - "!python/**"
       - "!screenshot/**"
-  # opencode runtime bundled by scripts/bundle-opencode.mjs.
-  - from: build/opencode-ai/
-    to: opencode-ai/
 afterPack: ./scripts/after-pack.cjs
 
 asar: true