docs: premium UI improvements — navbar links, hover effects, inline tips, accordion troubleshooting (#646)

- Move Discord, GitHub, PyPI, and Follow on X links from sidebar anchors to top-right navbar
- Lock dark mode as default via appearance.strict and hide theme toggle
- Add custom.css with hover highlighting for tables, code blocks, cards, callouts, and inline code
- Move all Tips and Common Pitfalls sections inline next to their relevant content across all 25 reference docs
- Polish context.md: remove duplicates, condense callouts, upgrade Cookbooks to CardGroup
- Convert Troubleshooting and Performance Optimization sections in installation.md, cli-setup.md, explorer-setup.md, learning-more.md, and faq.md from plain headers to AccordionGroup
- Change navigation-hint Tip callouts to Info in concepts.md, faq.md, glossary.md, and modules.md

docs/docs.json

@@ -24,8 +24,10 @@
     }
   },
   "appearance": {
-    "default": "dark"
+    "default": "dark",
+    "strict": true
   },
+  "css": "/assets/custom.css",
   "background": {
     "color": {
       "dark": "#080C10",
@@ -206,41 +208,29 @@
           }
         ]
       }
-    ],
-    "global": {
-      "anchors": [
-        {
-          "anchor": "Discord",
-          "href": "https://discord.gg/sV34vps5hH",
-          "icon": "discord"
-        },
-        {
-          "anchor": "GitHub",
-          "href": "https://github.com/semantica-agi/semantica",
-          "icon": "github"
-        },
-        {
-          "anchor": "PyPI",
-          "href": "https://pypi.org/project/semantica/",
-          "icon": "python"
-        },
-        {
-          "anchor": "Follow on X",
-          "href": "https://x.com/BuildSemantica",
-          "icon": "x-twitter"
-        }
-      ]
-    }
+    ]
   },
   "navbar": {
     "links": [
       {
-        "label": "GitHub",
-        "href": "https://github.com/semantica-agi/semantica"
+        "label": "Discord",
+        "href": "https://discord.gg/sV34vps5hH",
+        "icon": "discord"
       },
       {
-        "label": "Discord",
-        "href": "https://discord.gg/sV34vps5hH"
+        "label": "GitHub",
+        "href": "https://github.com/semantica-agi/semantica",
+        "icon": "github"
+      },
+      {
+        "label": "PyPI",
+        "href": "https://pypi.org/project/semantica/",
+        "icon": "python"
+      },
+      {
+        "label": "Follow on X",
+        "href": "https://x.com/BuildSemantica",
+        "icon": "x-twitter"
       }
     ],
     "primary": {