Docs homepage and search polish

The docs site homepage now uses a flatter, calmer presentation, and local docs search has a clearer validation workflow. This change also removes long dash punctuation from visible docs copy so the writing reads cleaner and less template-like.

What changed

• docs-site/src/css/custom.css removes hero gradients, normalizes hero title spacing, and simplifies the eyebrow badge.
• docs-site/src/pages/index.module.css tightens homepage feature cards with an 8px radius, quieter hover states, and more compact spacing.
• docs-site/docusaurus.config.ts keeps local Docusaurus search, adds page indexing, expands result limits and context, and excludes navbar, footer, breadcrumbs, pagination, table of contents, and doc footer chrome from the index.
• docs-site/package.json adds preview:search for the production-search workflow: build the docs site, then serve the generated static output.
• Current docs, versioned docs, and blog posts replace long dash separators with cleaner punctuation or explicit wording.

User impact

• The docs homepage has a flat visual style with no gradient coloring.
• Search validation is less confusing: pnpm start remains for live editing, while pnpm serve or pnpm preview:search validates the generated search index.
• Searching for terms such as tele in the built site returns real local results instead of the build-index warning.
• The visible docs copy no longer uses em dash or en dash separators.

Verification

Checked locally with:

cd docs-site
pnpm typecheck
pnpm build
rg -n '\x{2014}|\x{2013}' docs-site/docs docs-site/versioned_docs docs-site/blog docs-site/src/pages docs-site/docusaurus.config.ts
rg -n 'linear-gradient|radial-gradient' docs-site/src

The built site was served at http://127.0.0.1:3001/. Browser checks confirmed the homepage hero has no background image, the mobile layout fits at 390px, and searching for tele returns Telemetry results without the build-index warning.