fix(opencode): avoid hook listener leaks and Windows popups

[dvd233]

Summary

• replace the generated OpenCode hook's Bun Response stdin bridge with Node child_process.spawn
• pass windowsHide: true on Windows and swallow child-process failures
• remove per-dispatch listeners after completion and cover repeated dispatches with a regression test

Validation

• npx vitest run src/__tests__/opencode-hooks.test.ts --reporter=verbose
• npx tsc --noEmit
• npm run build
• node dist/index.js --version

Fixes #673

[github-actions]

• [P1 blocking] Handle errors from the stdin pipe — src/opencode-hooks.ts:119: child.stdin is a separate Writable; if teamai exits or closes stdin early, it can emit an error such as EPIPE. The child’s error listener does not catch stream errors, so this may become an uncaught exception and disrupt OpenCode. Add a stdin error handler and settle the promise safely.
• [P1 blocking] Provide a real feature-level end-to-end verification record — The PR description lists a unit test, typecheck, build, and --version smoke test, but never installs/runs the generated OpenCode plugin or verifies hook dispatch and Windows failure behavior through the real CLI. This does not satisfy the required e2e test plan/record.