Initial iris repository structure

WASM reactive UI framework for Go:
- reactive/ - Signal[T], Effect, Runtime
- ui/ - Button, Text, Input, View, Canvas, SVG components
- navigation/ - Router, guards, history management
- auth/ - OIDC client for WASM applications
- host/ - Static file server

Extracted from arcadia as open-source component.

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

ui/canvas_config.go

@@ -0,0 +1,51 @@
+//go:build js && wasm
+
+package ui
+
+// CanvasDefaults contains default values for canvas rendering and interaction
+type CanvasDefaults struct {
+	// Interaction thresholds
+	EdgeThreshold float64 // Distance from edge to trigger connection drawing (default: 15)
+	DragThreshold float64 // Minimum movement to count as drag vs click (default: 2)
+
+	// Resize constraints
+	MinResizeWidth  float64 // Minimum width when resizing (default: 100)
+	MinResizeHeight float64 // Minimum height when resizing (default: 100)
+
+	// Resize handle sizes
+	CornerHandleSize float64 // Size of corner resize handles (default: 12)
+	EdgeHandleWidth  float64 // Width of edge resize handles (default: 8)
+	EdgeHandleLength float64 // Length of edge resize handles (default: 24)
+
+	// Connection rendering
+	ConnectionHitWidth    float64 // Width of invisible hit area for connections (default: 12)
+	LabelBackgroundWidth  float64 // Width of label background rect (default: 60)
+	LabelBackgroundHeight float64 // Height of label background rect (default: 20)
+
+	// Container layout
+	ContainerHeaderHeight float64 // Height of container header bar for click detection (default: 32)
+}
+
+// DefaultCanvasDefaults returns the default configuration values
+var DefaultCanvasDefaults = CanvasDefaults{
+	// Interaction thresholds
+	EdgeThreshold: 15.0,
+	DragThreshold: 2.0,
+
+	// Resize constraints
+	MinResizeWidth:  100.0,
+	MinResizeHeight: 100.0,
+
+	// Resize handle sizes
+	CornerHandleSize: 12.0,
+	EdgeHandleWidth:  8.0,
+	EdgeHandleLength: 24.0,
+
+	// Connection rendering
+	ConnectionHitWidth:    12.0,
+	LabelBackgroundWidth:  60.0,
+	LabelBackgroundHeight: 20.0,
+
+	// Container layout
+	ContainerHeaderHeight: 32.0,
+}