feat: create ai-elements-ui demo application

Demo app showcasing ai-elements-ui components:
- AI Canvas with resizable split-panel layout
- Conversation history sidebar
- Avatar with animated states (idle, thinking, speaking)
- Typing indicators (dots, pulse, wave variants)
- Confidence meters (bar, gauge, dots, ring variants)
- Code blocks with syntax highlighting
- Skeleton loaders for various content types

Uses base-ui design tokens and Apple theme for styling.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package-lock.json

@@ -8,6 +8,7 @@
       "name": "ai-elements-demo",
       "version": "0.0.0",
       "dependencies": {
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         "@angular/common": "^19.2.0",
         "@angular/compiler": "^19.2.0",
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@@ -15,6 +16,8 @@
         "@angular/platform-browser": "^19.2.0",
         "@angular/platform-browser-dynamic": "^19.2.0",
         "@angular/router": "^19.2.0",
+        "ai-elements-ui": "file:../ai-elements-ui/dist",
+        "base-ui": "file:../sda-frontend/libs/base-ui/dist",
         "rxjs": "~7.8.0",
         "tslib": "^2.3.0",
         "zone.js": "~0.15.0"
@@ -33,6 +36,46 @@
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       }
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+    "../ai-elements-ui/dist": {
+      "name": "ai-elements-ui",
+      "version": "0.1.0",
+      "license": "MIT",
+      "dependencies": {
+        "tslib": "^2.3.0"
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+      "peerDependencies": {
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+        "@angular/common": "^19.0.0",
+        "@angular/core": "^19.0.0",
+        "@angular/forms": "^19.0.0",
+        "@angular/platform-browser": "^19.0.0",
+        "@angular/router": "^19.0.0",
+        "base-ui": "^0.1.0",
+        "rxjs": "^7.8.0"
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+      "license": "MIT",
+      "dependencies": {
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@@ -6003,6 +6063,10 @@
         "node": ">= 14"
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     "node_modules/ajv": {
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@@ -6276,6 +6340,10 @@
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       "license": "MIT"
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+    "node_modules/base-ui": {
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