fix(tui): keep task preview output fresh

[PaiduiXiaowangzi]

Related Issue

Resolve #2341

Problem

The selected task's Preview Output was loaded only when the selection changed. Output from a running process task could remain stale, manual refresh updated only task metadata, and output-loading failures looked identical to a task that produced no output.

What changed

• Refresh the selected process-task preview while it is running and fetch final output when it reaches a terminal state.
• Make manual refresh and stop flows retry the selected preview while preventing overlapping or stale requests from overwriting the current task.
• Render preview-loading failures as a distinct retryable error state.
• Add contract tests for live refresh, terminal output, retry recovery, error rendering, and late-response isolation.

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

[changeset-bot]

🦋 Changeset detected

Latest commit: a725bc4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Patch

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