fix: satisfy Ponytail lint and type checks

[o-az]

Summary

• make the Ponytail plugin pass the repository’s strict oxlint rules without weakening the CLI lint gate
• tighten parser, event-result, and test-harness types for the new project typecheck
• preserve native Ponytail commands, per-thread modes, configuration behavior, and single-file bundling

Verification

• bun oxlint --deny=all plugins tests/ponytail-plugin.test.ts
• bun tsc --project tsconfig.json
• bun test tests/ponytail-plugin.test.ts
• bun build plugins/ponytail.ts --outdir <temporary-directory>
• git diff --check