chore(docs): Upgrade to Astro 6

[Lms24]

Upgrades our docs to newly released Astro 6:

• Upgraded astro from 5.16.15 to 6.0.2 and @astrojs/svelte from 7.2.5 to 8.0.0 via npx @astrojs/upgrade
• Changed z import in docs/src/content.config.ts from astro:content to astro/zod (deprecated in Astro 6)
• Replaced deprecated @astrojs/tailwind integration with @tailwindcss/vite plugin in docs/astro.config.mjs
• Migrated Tailwind v3 JS config (docs/tailwind.config.mjs) to Tailwind v4 CSS-based config (@theme/@theme inline/@utility directives in docs/src/styles/global.css)

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

📋 Changelog Preview

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Entries from this PR are highlighted with a left border (blockquote style).

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New Features ✨

Attributes

• Add remaining TTFB, FCP and FP web vital attributes by Lms24 in #235
• Add LCP web vital meta attributes by Lms24 in #233
• Add CLS web vital source attribute by Lms24 in #234
• Add core web web vital value attributes by Lms24 in #229
• Add allow_any_value field to attribute schema by vgrozdanic in #272

Other

• (http) Add http.server.request.time_in_queue attribute by dingsdax in #267
• (resource) Add resource.deployment.environment by mjq in #266
• Add sentry.timestamp.sequence attribute to the spec by logaretm in #262
• Add changelog tracking to attribute definitions by ericapisani in #270

Bug Fixes 🐛

• (attributes) Remove allow_any_value boolean attribute and allow any as type by vgrozdanic in #273
• (gen_ai) Input and output token description by obostjancic in #261
• Don't run changelog generation on yarn generate by Lms24 in #277
• Avoid changelog generation recursion by Lms24 in #274

Documentation 📚

• Update README with up-to-date links by ericapisani in #258

Internal Changes 🔧

Deps

• Bump dompurify from 3.3.1 to 3.3.2 by dependabot in #278
• Bump svgo from 3.3.2 to 3.3.3 by dependabot in #275
• Bump svelte from 5.51.5 to 5.53.5 by dependabot in #271
• Bump rollup from 4.40.1 to 4.59.0 by dependabot in #269
• Bump svelte from 5.48.1 to 5.51.5 by dependabot in #260

Deps Dev

• Bump tar from 7.5.8 to 7.5.10 by dependabot in #276
• Bump tar from 7.5.7 to 7.5.8 by dependabot in #259

Other

• (ai) Deprecate rest of ai.* attributes by constantinius in #264
• (attributes) Ensure each attribute json has a changelog entry by Lms24 in #282

• (docs) Upgrade to Astro 6 by Lms24 in #283

• (gen_ai) Deprecate gen_ai.tool.input, gen_ai.tool.message, gen_ai.tool.output by constantinius in #265
• (repo) Populate changelog property when running yarn create:attribute by Lms24 in #280

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