Fix SeoPanel pending draft flush

[richardjoo]

What does this PR do?

Fixes SeoPanel so pending debounced SEO text edits are still emitted when the panel unmounts or content switches before the debounce timer fires.

Closes #

Type of change

• Bug fix
• Feature (requires maintainer-approved Discussion)
• Refactor (no behavior change)
• Translation
• Documentation
• Performance improvement
• Tests
• Chore (dependencies, CI, tooling)

Checklist

• I have read CONTRIBUTING.md
• pnpm typecheck passes
• pnpm lint passes
• pnpm test passes (or targeted tests for my change)
• pnpm format has been run
• I have added/updated tests for my changes (if applicable)
• User-visible strings in the admin UI are wrapped for translation (if applicable). Do not include messages.po changes except in translation PRs — a workflow extracts catalogs on merge to main.
• I have added a changeset (if this PR changes a published package)
• New features link to an approved Discussion: https://github.com/emdash-cms/emdash/discussions/...

AI-generated code disclosure

• This PR includes AI-generated code — model/tool: GPT-5.4 / OpenCode

Screenshots / test output

• pnpm --filter @emdash-cms/admin test
• pnpm format:check

[changeset-bot]

⚠️ No Changeset found

Latest commit: 5d680f5

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[Copilot]

Pull request overview

Fixes SeoPanel so any pending debounced SEO text edits are flushed (emitted via onChange) when the panel unmounts or when the editor switches to a different contentKey before the debounce timer fires.

Changes:

• Update flushPendingDraft() to cancel any pending timer and avoid emitting when the current draft matches the last emitted snapshot.
• Strengthen the unmount-flush test to assert the flushed value is the final emitted call and that no later debounce emits occur.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/admin/src/components/SeoPanel.tsx	Ensures pending debounced draft updates are flushed safely on unmount/content switch without redundant emits.
packages/admin/tests/components/SeoPanel.test.tsx	Verifies pending debounced edits are flushed on unmount and no additional emits happen after the debounce window.

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