feat(web): Phase 11 UI/UX — TOC, dark mode toggle, /docs index

- Install rehype-slug (proper heading anchors) + github-slugger (matching TOC)
- TOC component: auto-generated from h2/h3 headings, clickable anchors
- Dark mode toggle: ThemeToggle (localStorage + system default), class-based
- /docs index page (lists all docs by section)
- Markdown.tsx uses rehype-slug for stable heading ids
- globals.css: @custom-variant dark (.dark class) for class-based dark mode
- layout.tsx: nav includes ThemeToggle

Note: per user instruction, installed real deps (rehype-slug, github-slugger,
@types/hast) instead of hacky inline any-cast hacks.

bun.lock

@@ -55,13 +55,16 @@
       "dependencies": {
         "@mcpedia/config": "workspace:*",
         "@mcpedia/core": "workspace:*",
+        "github-slugger": "^2.0.0",
         "next": "16.3.1",
         "react": "19.2.8",
         "react-dom": "19.2.8",
         "react-markdown": "^9.0.0",
+        "rehype-slug": "^6.0.0",
       },
       "devDependencies": {
         "@tailwindcss/postcss": "^4",
+        "@types/hast": "^3.0.5",
         "@types/node": "^20",
         "@types/react": "^19",
         "@types/react-dom": "^19",
@@ -879,6 +882,8 @@
 
     "get-tsconfig": ["get-tsconfig@4.14.3", "", { "dependencies": { "resolve-pkg-maps": "^1.0.0" } }, "sha512-++QEw4DIY7WGoukz+/+A/8dGYPT9l9yIadnmSgZ8Rjr3YVSVDipQSO9CdnJo9ePqFqUUqh+wk9uIaoiAwsiPkA=="],
 
+    "github-slugger": ["github-slugger@2.0.0", "", {}, "sha512-IaOQ9puYtjrkq7Y0Ygl9KDZnrf/aiUJYUpVf89y8kyaxbRG7Y1SrX/jaumrv81vc61+kiMempujsM3Yw7w5qcw=="],
+
     "glob-parent": ["glob-parent@6.0.2", "", { "dependencies": { "is-glob": "^4.0.3" } }, "sha512-XxwI8EOhVQgWp6iDL+3b0r86f4d6AX6zSU55HfB4ydCEuXLXc5FcYeOu+nnGftS4TEju/11rt4KJPTMgbfmv4A=="],
 
     "globals": ["globals@16.4.0", "", {}, "sha512-ob/2LcVVaVGCYN+r14cnwnoDPUufjiYgSqRhiFD0Q1iI4Odora5RE8Iv1D24hAz5oMophRGkGz+yuvQmmUMnMw=="],
@@ -905,8 +910,12 @@
 
     "hasown": ["hasown@2.0.4", "", { "dependencies": { "function-bind": "^1.1.2" } }, "sha512-T2UbfbBEF32wiepXIsMlTW9+dDYC6wMh/t/vYA4tuOMKqWz/n3vr1NFSxQiyP+zk2mXsoMA/i/7qV6LKut1t1A=="],
 
+    "hast-util-heading-rank": ["hast-util-heading-rank@3.0.0", "", { "dependencies": { "@types/hast": "^3.0.0" } }, "sha512-EJKb8oMUXVHcWZTDepnr+WNbfnXKFNf9duMesmr4S8SXTJBJ9M4Yok08pu9vxdJwdlGRhVumk9mEhkEvKGifwA=="],
+
     "hast-util-to-jsx-runtime": ["hast-util-to-jsx-runtime@2.3.6", "", { "dependencies": { "@types/estree": "^1.0.0", "@types/hast": "^3.0.0", "@types/unist": "^3.0.0", "comma-separated-tokens": "^2.0.0", "devlop": "^1.0.0", "estree-util-is-identifier-name": "^3.0.0", "hast-util-whitespace": "^3.0.0", "mdast-util-mdx-expression": "^2.0.0", "mdast-util-mdx-jsx": "^3.0.0", "mdast-util-mdxjs-esm": "^2.0.0", "property-information": "^7.0.0", "space-separated-tokens": "^2.0.0", "style-to-js": "^1.0.Line truncated
 
+    "hast-util-to-string": ["hast-util-to-string@3.0.1", "", { "dependencies": { "@types/hast": "^3.0.0" } }, "sha512-XelQVTDWvqcl3axRfI0xSeoVKzyIFPwsAGSLIsKdJKQMXDYJS4WYrBNF/8J7RdhIcFI2BOHgAifggsvsxp/3+A=="],
+
     "hast-util-whitespace": ["hast-util-whitespace@3.0.0", "", { "dependencies": { "@types/hast": "^3.0.0" } }, "sha512-88JUN06ipLwsnv+dVn+OIYOvAuvBMy/Qoi6O7mQHxdPXpjy+Cd6xRkWwux7DKO+4sYILtLBRIKgsdpS2gQc7qw=="],
 
     "hermes-estree": ["hermes-estree@0.25.1", "", {}, "sha512-0wUoCcLp+5Ev5pDW2OriHC2MJCbwLwuRx+gAqMTOkGKJJiBCLjtrvy4PWUGn6MIVefecRpzoOZ/UV6iGdOr+Cw=="],
@@ -1271,6 +1280,8 @@
 
     "regexp.prototype.flags": ["regexp.prototype.flags@1.5.4", "", { "dependencies": { "call-bind": "^1.0.8", "define-properties": "^1.2.1", "es-errors": "^1.3.0", "get-proto": "^1.0.1", "gopd": "^1.2.0", "set-function-name": "^2.0.2" } }, "sha512-dYqgNSZbDwkaJ2ceRd9ojCGjBq+mOm9LmtXnAnEGyHhN/5R7iDW2TRw3h+o/jCFxus3P2LfWIIiwowAjANm7IA=="],
 
+    "rehype-slug": ["rehype-slug@6.0.0", "", { "dependencies": { "@types/hast": "^3.0.0", "github-slugger": "^2.0.0", "hast-util-heading-rank": "^3.0.0", "hast-util-to-string": "^3.0.0", "unist-util-visit": "^5.0.0" } }, "sha512-lWyvf/jwu+oS5+hL5eClVd3hNdmwM1kAC0BUvEGD19pajQMIzcNUd/k9GsfQ+FfECvX+JE+e9/btsKH0EjJT6A=="],
+
     "remark-parse": ["remark-parse@11.0.0", "", { "dependencies": { "@types/mdast": "^4.0.0", "mdast-util-from-markdown": "^2.0.0", "micromark-util-types": "^2.0.0", "unified": "^11.0.0" } }, "sha512-FCxlKLNGknS5ba/1lmpYijMUzX2esxW5xQqjWxw2eHFfS2MSdaHVINFmhjo+qN1WhZhNimq0dZATN9pH0IDrpA=="],
 
     "remark-rehype": ["remark-rehype@11.1.2", "", { "dependencies": { "@types/hast": "^3.0.0", "@types/mdast": "^4.0.0", "mdast-util-to-hast": "^13.0.0", "unified": "^11.0.0", "vfile": "^6.0.0" } }, "sha512-Dh7l57ianaEoIpzbp0PC9UKAdCSVklD8E5Rpw7ETfbTl3FqcOOgq5q2LVDhgGCkaBv7p24JXikPdvhhmHvKMsw=="],