feat: support OpenCode v2 quota wait

[azumag]

Summary

• add the OpenCode v2 default plugin definition used by the Web/server runtime
• override 429 retries with the configured cooldown and resume the same prompt after OpenCode's native retry ceiling
• publish this breaking entry-point change as 2.0.0 under the v2 dist-tag, leaving v1 users on 1.x

Validation

• npm run typecheck
• npx vitest run --exclude __tests__/config/watcher.test.ts (694 passed, 11 skipped)
• npm test -- __tests__/v2.test.ts (3 passed)
• npm run build
• npm package dry-run and built default-export shape check
• Computer-use E2E in the reported Web session: observed configured retry countdown, a second 60-second attempt, and with a temporary 1-second cooldown verified automatic resume beyond the native five-attempt ceiling

Existing environment note

The full local suite reaches 703 passing tests but the six existing ConfigWatcher timing tests fail on this host because fs.watch returns EMFILE (system file-watcher exhaustion). The changed v2 tests and the rest of the suite pass.