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_errors.go

@@ -0,0 +1,36 @@
+//go:build js && wasm
+
+package ui
+
+import "log"
+
+// CanvasWarning represents a type of canvas warning
+type CanvasWarning int
+
+const (
+	WarnItemNotFound CanvasWarning = iota
+	WarnConnectionNotFound
+	WarnInvalidOperation
+	WarnSelfConnection
+	WarnMissingCallback
+)
+
+// warningNames maps warning types to human-readable names
+var warningNames = map[CanvasWarning]string{
+	WarnItemNotFound:       "ItemNotFound",
+	WarnConnectionNotFound: "ConnectionNotFound",
+	WarnInvalidOperation:   "InvalidOperation",
+	WarnSelfConnection:     "SelfConnection",
+	WarnMissingCallback:    "MissingCallback",
+}
+
+// LogCanvasWarning logs a warning for recoverable canvas issues.
+// These are situations where the operation cannot complete but the
+// application can continue safely.
+func LogCanvasWarning(warn CanvasWarning, format string, args ...any) {
+	name := warningNames[warn]
+	if name == "" {
+		name = "Unknown"
+	}
+	log.Printf("[Canvas %s] "+format, append([]any{name}, args...)...)
+}