test: expand markdown and table logic coverage

[zbeyens]

Summary

• deepen non-React markdown logic coverage and fix incomplete MDX fallback when a parsed prefix ends in a void block
• add focused table lib coverage for merge, split, expanded row/column deletion, sizing, and selection movement
• include the current checkout's existing task-skill docs and useSlateProps test updates as-is

Testing

• bun test packages/markdown/src
• bun run test:slowest -- --top 15 packages/markdown/src
• bun test packages/table/src/lib/merge/tableMergeBehavior.spec.tsx packages/table/src/lib/transforms/tableSelectionAndSizing.spec.tsx
• bun test packages/table/src/lib
• bun run test:slowest -- --top 15 packages/table/src/lib
• pnpm install
• pnpm turbo typecheck --filter=./packages/table
• pnpm lint:fix

Notes

• pnpm turbo build --filter=./packages/markdown and pnpm turbo build --filter=./packages/table are blocked by an external rolldown / Node 20.12.1 node:util.styleText failure in transitive build work, not by the package changes here.
• bun check was not run before opening this PR because it was explicitly skipped.

Post-Deploy Monitoring & Validation

No additional operational monitoring required. This PR is test/doc heavy, and the only runtime change is a narrow markdown fallback fix covered by package tests.

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Project	Deployment	Actions	Updated (UTC)
plate	Ready	Preview, Comment	Mar 15, 2026 9:14pm

[changeset-bot]

🦋 Changeset detected

Latest commit: 327adce

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

This PR includes changesets to release 2 packages

Name	Type
@platejs/markdown	Patch
@platejs/ai	Patch

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