Improve Testream reporter search snippets

[hasanalituran]

Summary

Expands the meta descriptions for the Vitest, Cypress, and Playwright reporter guides so they describe the existing reporting, evidence, and CI-upload capabilities more completely.

Evidence and affected URLs

• Fresh Google Search Console data for 2026-07-11 to 2026-07-17 shows impressions for https://docs.testream.app/reporters/vitest, https://docs.testream.app/reporters/cypress, and https://docs.testream.app/reporters/playwright.
• Fresh live checks found their existing descriptions were short relative to the substantive guide content; the updated text remains specific to documented capabilities.

Validation performed

• npm run build (Docusaurus production build)
• git diff --check

Risks and data gaps

• Metadata changes can affect snippets after deployment, but Google controls the displayed snippet.
• Search Console data is subject to the normal reporting lag.
• Bing Webmaster UI diagnostics and AI Performance could not be extracted in the authenticated browser session; API and live-host evidence were used where available.

Manual tasks for Hasan

• Approve the copy changes before merge.
• Merge and deploy the docs site through the normal GitHub Pages workflow.
• After deployment, verify the three live descriptions and request re-crawl/re-indexing in Google Search Console and Bing Webmaster if desired.