feat: add Building with AI page (#179)

## Summary
- New documentation page at **Get started > Overview > Building with
AI** (before FAQ)
- Helps developers use AI coding assistants (Claude Code, Cursor,
Windsurf) with the Grid API
- Covers: skill installation, credential setup, example prompts by use
case, CLI command reference, llms.txt discovery, and tips for best
results
- Uses custom FeatureCard components with new Central Icons
(magnifying-glass, prompt, arrow-path-right, bug, console-sparkle)

## Test plan
- [x] Page renders at `/platform-overview/building-with-ai`
- [x] Appears in sidebar under Overview, before FAQ
- [x] Sidebar icon (console-sparkle) renders correctly
- [x] FeatureCards display with colored icons
- [x] Code blocks, tables, and Tip component render properly
- [x] Internal links (`/llms.txt`, `/llms-full.txt`) work

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Jeremy Klein <jklein24@gmail.com>
Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

Author: 4 people

.gitignore

@@ -48,3 +48,6 @@ figma-*.md
 
 # Personal todo files
 TODO-*.md
+
+# Icon build script (local tool, requires license key)
+scripts/export-icons.js

mintlify/docs.json

@@ -44,6 +44,7 @@
               "platform-overview/introduction/what-is-grid",
               "platform-overview/capabilities",
               "platform-overview/use-cases",
+              "platform-overview/building-with-ai",
               "platform-overview/introduction/faq"
             ]
           },