Revamp the guides section: taxonomy, single-page structure, and new landing/filter UX (#25338)

## What

A full revamp of the `/guides` section — taxonomy, structure, and UX.

Preview: https://deploy-preview-25338--docsdocker.netlify.app/guides/

### Taxonomy & structure
- Replaces the sprawling 24-tag set with a focused 9-tag taxonomy
aligned to use case / SDLC: **Languages & frameworks, AI, Testing,
CI/CD, Security, Databases, Deployment, Admin, Hands-on labs**.
- Removes the languages taxonomy entirely (`data/languages.yaml` and all
`languages:` front matter).
- Collapses all multi-page guide series into single pages, with aliases
so old sub-page URLs continue to resolve.
- Deletes redirect-only shim pages and flattens directory-wrapped single
pages.

### Landing page (`/guides/`)
- A clean index: hero, then category sections listing each guide as a
plain **title / summary** row.
- **Browse rail** (sticky, left): click a topic to filter the page to
just that topic's guides; "All guides" resets. A count + Clear bar
appears while filtering.
- **Text filter**: instant client-side search over title, summary, and
tags. Topic filter and text search are mutually exclusive and share the
same flat-list view.
- No more "Featured guides" section.

### Guide content pages
- Removes the left sidebar for the guides section (mobile drawer kept).
- Centered reading column (`92ch`) with the TOC taking the remaining
width.
- Summary rendered as a lead paragraph under the h1.
- TOC scrollbar auto-hides until hover; breadcrumbs render at a
consistent size inside and outside `prose`.

## Notes
- Deep full-text search across guide bodies is still handled by the
existing site-wide Pagefind (⌘K); the landing filter is the fast
metadata-narrowing surface.
- `series.html` is retained — it's still used by `get-started` pages.

## Validation
- Site builds clean locally (Hugo dev server, no errors / broken refs).
- All collapsed sub-page URLs redirect via aliases.

## Follow-ups

- Prune guides that we no longer need/want
- Tighten the guides that span too many concepts (e.g. language guides;
remove cicd/deploy/sscs)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dvdksn

assets/css/utilities.css

@@ -208,6 +208,33 @@
     }
   }
 }
+@utility scrollbar-hover {
+  /* Firefox: hide the thumb until hover */
+  scrollbar-width: thin;
+  scrollbar-color: transparent transparent;
+  &:hover {
+    scrollbar-color: var(--color-gray-400) transparent;
+  }
+  .dark &:hover {
+    scrollbar-color: var(--color-gray-600) transparent;
+  }
+  /* WebKit: reserve the track, reveal the thumb only on hover */
+  &::-webkit-scrollbar {
+    width: 8px;
+    height: 8px;
+  }
+  &::-webkit-scrollbar-thumb {
+    border-radius: 9999px;
+    background-color: transparent;
+  }
+  &:hover::-webkit-scrollbar-thumb {
+    background-color: var(--color-gray-400);
+  }
+  .dark &:hover::-webkit-scrollbar-thumb {
+    background-color: var(--color-gray-600);
+  }
+}
+
 @utility chip {
   @apply border-divider-light dark:border-divider-dark inline-flex items-center gap-1 rounded-full border bg-gray-100 px-2 text-sm text-gray-800 select-none dark:bg-gray-700 dark:text-gray-200;
 }
@@ -217,7 +244,17 @@
 }
 
 @utility breadcrumbs {
-  font-size: 90%;
+  /* Absolute size so breadcrumbs render identically inside and outside prose */
+  font-size: calc(var(--text-base) * 0.9);
+}
+
+/* Guides landing: collapse section spacing into a flat list while filtering.
+   Grouped spacing is the static default; this only applies once the page is
+   being filtered, so it never affects first paint (no layout jank). */
+.guides-flat > section {
+  border-top-width: 0 !important;
+  padding-top: 0 !important;
+  padding-bottom: 0 !important;
 }
 
 @utility topbar-button {

content/guides/_index.md

@@ -1,21 +1,25 @@
 ---
 title: Docker guides
 linkTitle: Guides
-description: Explore the Docker guides
+description: Step-by-step tutorials, organized by what you're trying to do.
 keywords: docker, guides, tutorials, learning paths, getting started
 params:
   icon: book-open
 layout: landing
 aliases:
   - /guides/language/
   - /language/
+  - /guides/dhi-from-doi/
+  - /guides/dhi-from-wolfi/
+  - /guides/dhi-go-example/
+  - /guides/dhi-nodejs-example/
+  - /guides/dhi-python-example/
+  - /guides/lab-docker-for-ai-redirect/
   - /learning-paths/
 ---
 
-Explore our collection of guides to learn how Docker can optimize your
-development workflows and how to use it with specific languages, frameworks, or
-technologies.
+Explore guides to learn how Docker can optimize your development workflows and
+how to use it with specific languages, frameworks, or technologies.
 
 Can't find the guide you're looking for? Open an issue on the
-[docker/docs](https://github.com/docker/docs/issues/new) repository to let us
-know.
+[docker/docs](https://github.com/docker/docs/issues/new) repository.