feat: add Pi agent blog post, AI tooling, and SVG support

Add new blog post documenting a week using the Pi CLI agent for 100% agentic development. Include AI agent configuration with custom prompts and skills to streamline content creation workflow.

- Publish "Week with my-pi-agent" article with Pi logo and screenshot assets
- Add .pi/ configuration with new-blog-post prompt and review-article skill
- Create AGENTS.md with comprehensive project documentation for AI assistants
- Fix SVG rendering to skip unsupported dimension extraction in markdown filter
- Update picture generator to handle SVG files with simple img tag
- Update syntect dependency to 5.3.0 with default-fancy features
- Swap featured segment from older post to new Pi agent article

static/images/uploads/pi-logo.svg

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 800 800">
+  <!-- P shape: outer boundary clockwise, inner hole counter-clockwise -->
+  <path fill="#fff" fill-rule="evenodd" d="
+    M165.29 165.29
+    H517.36
+    V400
+    H400
+    V517.36
+    H282.65
+    V634.72
+    H165.29
+    Z
+    M282.65 282.65
+    V400
+    H400
+    V282.65
+    Z
+  "/>
+  <!-- i dot -->
+  <path fill="#fff" d="M517.36 400 H634.72 V634.72 H517.36 Z"/>
+</svg>