fix(runtime): sync CDN CSS version

[demtario]

Summary

Task: https://app.clickup.com/t/9015210959/DEV-2103

• rewrite baked Handsontable unpkg CSS links when a selected semver changes
• apply the shared transform in Sandpack, container, and authoring version flows
• cover root and Angular-style HTML paths plus pkg.pr.new no-op behavior

Test plan

• pnpm test
• pnpm --filter @handsontable/demo-runtime typecheck
• pnpm --filter @handsontable/demo-editor-shell typecheck
• pnpm --filter @handsontable/demo-authoring typecheck
• Manually switched the 18.0 docs Sparkline example to 17.1.0; verified its package dependencies, CDN CSS URL, and Sandpack preview

PR intentionally merged into another feature branch, to not break production logic with partial changes.

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Note

Low Risk
Localized, pure string rewrite on demo file maps with tests; no auth or persistence changes beyond keeping preview assets in sync.

Overview
Fixes a version-switch bug where npm deps were repinned but baked unpkg CSS in HTML stayed on the old semver, so previews could load mismatched JS and styles.

Adds applyHandsontableCss, which rewrites unpkg.com/handsontable@…/dist/handsontable.full.min.css in /index.html or /src/index.html to match the selected version. It is a no-op for pkg.pr.new builds (not on unpkg) and returns the input unchanged when there is nothing to rewrite.

The transform is chained after applyHandsontableVersion in authoring (version useEffect, including HTML in the “no change” check), SandpackRuntime, and ContainerRuntime, and is exported from @handsontable/demo-runtime. runner/pipeline/version.test.mjs covers root vs src/ HTML and the no-op cases.

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