docs: docusaurus setup (#3541)

# What does this PR do?

- Docusaurus server setup
- Deprecates Sphinx build pipeline
- Deprecates remaining references to Readthedocs
- MDX compile errors and broken links to be addressed in follow-up PRs

<!-- Provide a short summary of what this PR does and why. Link to relevant issues if applicable. -->

<!-- If resolving an issue, uncomment and update the line below -->

<!-- Closes #[issue-number] -->

## Test Plan

```
npm install
npm gen-api-docs all
npm run build
```

<!-- Describe the tests you ran to verify your changes with result summaries. *Provide clear instructions so the plan can be easily re-executed.* -->

docs/docusaurus.config.ts

@@ -0,0 +1,230 @@
+// @ts-check
+// Note: type annotations allow type checking and IDEs autocompletion
+
+import type * as Preset from "@docusaurus/preset-classic";
+import type { Config } from "@docusaurus/types";
+import type * as Plugin from "@docusaurus/types/src/plugin";
+import type * as OpenApiPlugin from "docusaurus-plugin-openapi-docs";
+
+const config: Config = {
+  title: 'Llama Stack',
+  tagline: 'The open-source framework for building generative AI applications',
+  url: 'https://reluctantfuturist.github.io',
+  baseUrl: '/llama-stack/',
+  onBrokenLinks: "warn",
+  onBrokenMarkdownLinks: "warn",
+  favicon: "img/favicon.ico",
+
+  // GitHub pages deployment config.
+  organizationName: 'reluctantfuturist',
+  projectName: 'llama-stack',
+  trailingSlash: false,
+
+  presets: [
+    [
+      "classic",
+      {
+        docs: {
+          sidebarPath: require.resolve("./sidebars.ts"),
+          // Please change this to your repo.
+          // Remove this to remove the "edit this page" links.
+          editUrl: 'https://github.com/meta-llama/llama-stack/tree/main/docs/',
+          docItemComponent: "@theme/ApiItem", // Derived from docusaurus-theme-openapi
+        },
+        blog: false,
+        theme: {
+          customCss: require.resolve("./src/css/custom.css"),
+        },
+      } satisfies Preset.Options,
+    ],
+  ],
+
+  themeConfig: {
+    image: 'img/llama-stack.png',
+    navbar: {
+      title: 'Llama Stack',
+      logo: {
+        alt: 'Llama Stack Logo',
+        src: 'img/llama-stack-logo.png',
+      },
+      items: [
+        {
+          type: 'docSidebar',
+          sidebarId: 'tutorialSidebar',
+          position: 'left',
+          label: 'Docs',
+        },
+        {
+          type: 'docSidebar',
+          sidebarId: 'apiSidebar',
+          position: 'left',
+          label: 'API Reference',
+        },
+        {
+          href: 'https://github.com/llamastack/llama-stack',
+          label: 'GitHub',
+          position: 'right',
+        },
+      ],
+    },
+    footer: {
+      style: 'dark',
+      links: [
+        {
+          title: 'Docs',
+          items: [
+            {
+              label: 'Getting Started',
+              to: '/docs/getting_started/quickstart',
+            },
+            {
+              label: 'Concepts',
+              to: '/docs/concepts',
+            },
+            {
+              label: 'API Reference',
+              to: '/docs/api/llama-stack-specification',
+            },
+          ],
+        },
+        {
+          title: 'Community',
+          items: [
+            {
+              label: 'Discord',
+              href: 'https://discord.gg/llama-stack',
+            },
+            {
+              label: 'GitHub Discussions',
+              href: 'https://github.com/llamastack/llama-stack/discussions',
+            },
+            {
+              label: 'Issues',
+              href: 'https://github.com/llamastack/llama-stack/issues',
+            },
+          ],
+        },
+        {
+          title: 'More',
+          items: [
+            {
+              label: 'GitHub',
+              href: 'https://github.com/llamastack/llama-stack',
+            },
+            {
+              label: 'PyPI',
+              href: 'https://pypi.org/project/llama-stack/',
+            },
+          ],
+        },
+      ],
+      copyright: `Copyright © ${new Date().getFullYear()} Meta Platforms, Inc. Built with Docusaurus.`,
+    },
+    prism: {
+      additionalLanguages: [
+        'ruby',
+        'csharp',
+        'php',
+        'java',
+        'powershell',
+        'json',
+        'bash',
+        'python',
+        'yaml',
+      ],
+    },
+    docs: {
+      sidebar: {
+        hideable: true,
+      },
+    },
+    // Language tabs for API documentation
+    languageTabs: [
+      {
+        highlight: "python",
+        language: "python",
+        logoClass: "python",
+      },
+      {
+        highlight: "bash",
+        language: "curl",
+        logoClass: "curl",
+      },
+      {
+        highlight: "javascript",
+        language: "nodejs",
+        logoClass: "nodejs",
+      },
+      {
+        highlight: "java",
+        language: "java",
+        logoClass: "java",
+      },
+    ],
+  } satisfies Preset.ThemeConfig,
+
+  plugins: [
+    [
+      "docusaurus-plugin-openapi-docs",
+      {
+        id: "openapi",
+        docsPluginId: "classic",
+        config: {
+          llamastack: {
+            specPath: "static/llama-stack-spec.yaml",
+            outputDir: "docs/api",
+            downloadUrl: "https://raw.githubusercontent.com/meta-llama/llama-stack/main/docs/static/llama-stack-spec.yaml",
+            sidebarOptions: {
+              groupPathsBy: "tag",
+              categoryLinkSource: "tag",
+            },
+          } satisfies OpenApiPlugin.Options,
+        } satisfies Plugin.PluginOptions,
+      },
+    ],
+  ],
+
+  themes: [
+    "docusaurus-theme-openapi-docs",
+    [
+      require.resolve("@easyops-cn/docusaurus-search-local"),
+      {
+        // Optimization for production
+        hashed: true,
+
+        // Language settings
+        language: ["en"],
+
+        // Content indexing settings
+        indexDocs: true,
+        indexBlog: false, // No blog in Llama Stack
+        indexPages: true,
+
+        // Route configuration
+        docsRouteBasePath: '/docs',
+
+        // Search behavior optimization for technical docs
+        searchResultLimits: 8,
+        searchResultContextMaxLength: 50,
+        explicitSearchResultPath: true,
+
+        // User experience enhancements
+        searchBarShortcut: true,
+        searchBarShortcutHint: true,
+        searchBarPosition: "right",
+
+        // Performance optimizations
+        ignoreFiles: [
+          "node_modules/**/*",
+        ],
+
+        // Exclude OpenAPI generated docs from search to avoid duplicates
+        searchContextByPaths: [
+          "docs",
+        ],
+      },
+    ],
+  ],
+};
+
+export default config;