fix(tui): point error diagnostics to export debug zip

[liruifengv]

Related Issue

No linked issue; this fixes stale diagnostic guidance shown after TUI session errors.

Problem

TUI session errors still told users to run kimi export <sessionId>, even though the in-TUI debug export workflow is now /export-debug-zip.

What changed

Updated the session error diagnostic hint to point at /export-debug-zip, adjusted the message-flow regression tests, added a patch changeset, and removed the root plan.md file per request.

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.

Validation

• pnpm exec vitest run apps/kimi-code/test/tui/kimi-tui-message-flow.test.ts
• pnpm exec oxlint --type-aware apps/kimi-code/src/tui/constant/feedback.ts apps/kimi-code/src/tui/controllers/session-event-handler.ts apps/kimi-code/test/tui/kimi-tui-message-flow.test.ts
• git diff --check
• Read-only diff audit found no internal identifiers

[changeset-bot]

🦋 Changeset detected

Latest commit: 7329791

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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Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

pnpm dlx https://pkg.pr.new/@moonshot-ai/kimi-code@7329791

npx https://pkg.pr.new/@moonshot-ai/kimi-code@7329791

commit: 7329791