Fix loading bar cleanup when tasks log messages - #8531

WHY are these changes introduced?

Calling outputInfo() or outputWarn() during an Ink task writes directly to stderr, leaving the loading bar behind when the task finishes.

WHAT is this pull request doing?

Send stderr logs through Ink's existing console interception so messages remain visible and the task UI clears correctly. Add regression coverage for info/warning logs, task cleanup, and results staying on stdout.

How to manually test your changes?

pnpm exec nx build cli-kit

node --input-type=module -e '
import {renderSingleTask} from "./packages/cli-kit/dist/public/node/ui.js";
import {outputInfo, outputWarn, outputResult, TokenizedString} from "./packages/cli-kit/dist/public/node/output.js";
import {setTimeout as sleep} from "node:timers/promises";
await renderSingleTask({title: new TokenizedString("Preparing the result"), task: async () => {
  await sleep(1000);
  outputInfo("Prepared an item");
  outputWarn("Sample warning");
}});
outputResult("Done");
'

Before	After

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add