Reorganize HighFive example into highfive/ subdirectory

**Structure Before:**
examples/
  ├── HighFive.py, HighFive.html, HighFive.wasm, HighFive.ll (loose files)
  ├── highfive.html (old duplicate)
  ├── tabs/Tabs.*
  └── textinput/TextInput.*

**Structure After:**
examples/
  ├── highfive/HighFive.*
  ├── tabs/Tabs.*
  └── textinput/TextInput.*

**Changes:**
- Moved all HighFive.* files to examples/highfive/ subdirectory
- Updated paths in HighFive.html: runtime/ → ../runtime/
- Removed old duplicate highfive.html file
- Now consistent with tabs/ and textinput/ structure

**Testing:**
Access via: http://localhost:8111/highfive/HighFive.html

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

Co-Authored-By: Claude <noreply@anthropic.com>

examples/highfive/HighFive.py

@@ -0,0 +1,26 @@
+"""
+HighFive counter component - Demonstrates reactive signals and event handlers.
+
+This component uses a signal to track state and an onclick handler to update it.
+"""
+
+from ritz.syntax import *
+
+
+@component
+def HighFive():
+    """A counter that tracks high fives."""
+    high_fives = signal(0)
+
+    def increment():
+        high_fives += 1
+
+    with Div(class_="high-five-app"):
+        with P():
+            yield "Give me a high five! ✋"
+
+        with P(class_="count"):
+            yield f"High fives: {high_fives}"
+
+        with Button(onclick=increment):
+            yield "High Five!"