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.

src/lib/generated-files.ts

@@ -3,7 +3,7 @@
  *
  * Inspects a run segment of chat messages (the slice from a user trigger
  * to its terminating assistant reply) and surfaces files the AI wrote /
- * edited via tool calls. The opencode chat surface uses these helpers to
+ * edited via tool calls. The coding chat surface uses these helpers to
  * power generated artifact and diff previews.
  */
 import { diffLines } from 'diff';