fix: resolve stale thumbnail caching and revert optional schema properties

demo/showcase.md

@@ -0,0 +1,331 @@
+---
+
+@section {
+  flex: 2
+}
+@column {
+  align: center
+}
+# SuperDeck {.heading}
+# Presentations Reimagined {.subheading}
+
+---
+
+## What is SuperDeck? {.heading}
+
+@column
+
+SuperDeck is a presentation framework that transforms how developers create slides.
+
+- Write slides in **Markdown** - familiar syntax, version-controlled
+- Render with **Flutter** - cross-platform, beautiful UI
+- Extend with **custom widgets** - interactive, live demos
+- Export to **PDF** - share anywhere
+
+---
+
+@column {
+  flex: 2
+  align: center_left
+}
+### Traditional Tools {.heading}
+
+@column {
+  flex: 3
+}
+
+#### PowerPoint/Keynote
+
+- Binary files, poor version control
+- Limited code formatting
+- No live components
+- Platform-dependent
+
+#### SuperDeck
+
+- Plain text Markdown
+- Git-friendly diffs
+- Live Flutter widgets
+- Runs everywhere Flutter runs
+
+---
+
+@section {
+  flex: 2
+}
+@column {
+  align: center
+}
+## "Write once, present anywhere. Version control everything." {.heading}
+
+##### The SuperDeck Philosophy {.subheading}
+
+---
+
+@column {
+  flex: 2
+  align: center_left
+}
+### Hot Reload {.heading}
+
+Edit your slides and see changes instantly - no rebuild needed.
+
+@column {
+  flex: 3
+}
+
+- **Live Preview** - Changes appear in milliseconds
+- **State Preserved** - Stay on current slide while editing
+- **Error Recovery** - Graceful handling of syntax errors
+- **Watch Mode** - CLI monitors file changes automatically
+
+---
+
+### Markdown Syntax {.heading}
+
+@column {
+  flex: 2
+}
+
+```markdown
+---
+
+## Slide Title {.heading}
+
+@column
+
+Your content here with **bold**
+and *italic* text.
+
+- Bullet points
+- Code blocks
+- Mermaid diagrams
+
+---
+```{.code}
+
+---
+
+@section
+
+@column {
+  flex: 1
+}
+## Layout System {.heading}
+
+How SuperDeck organizes content on slides.
+
+@section {
+  flex: 3
+  align: top_left
+}
+
+@column {
+  flex: 1
+}
+#### Sections
+
+Horizontal rows that divide the slide vertically.
+
+```markdown
+@section {
+  flex: 2
+}
+```
+
+@column {
+  flex: 1
+}
+#### Columns
+
+Vertical divisions within sections.
+
+```markdown
+@column {
+  flex: 3
+  align: center
+}
+```
+
+@column {
+  flex: 1
+}
+#### Blocks
+
+Content containers with markdown or widgets.
+
+```markdown
+@widget {
+  name: "chart"
+}
+```
+
+---
+
+## Layout Types {.heading}
+
+@column
+
+| Layout | Structure | Best For |
+|--------|-----------|----------|
+| Title | Single centered section | Opening, section dividers |
+| Standard | Title row + body row | Default content slides |
+| Two-Column | Side-by-side blocks | Comparisons, pros/cons |
+| Three-Column | Three equal blocks | Categories, options |
+| Title-Left | Title block + content | Feature highlights |
+| Quote | Centered large text | Key takeaways, transitions |
+| Table | Markdown table | Structured data comparisons |
+
+---
+
+### The Block System {.heading}
+
+@column
+
+SuperDeck uses three core block types:
+
+- **Content Blocks** (`@column`) - Render markdown text, lists, tables
+- **Widget Blocks** (`@widget`) - Embed custom Flutter components
+- **Built-in Widgets** (`@image`, `@dartpad`, `@qrcode`) - Pre-configured widgets
+
+Each block supports:
+- `flex` - Relative sizing (default: 1)
+- `align` - Content positioning (e.g., `center`, `top_left`)
+- `scrollable` - Enable overflow scrolling
+
+---
+
+### Build Pipeline {.heading}
+
+@column
+
+```mermaid
+flowchart LR
+    A["slides.md"] --> B["Parser"]
+    B --> C["Blocks"]
+    C --> D["Widgets"]
+    D --> E["Flutter UI"]
+    E --> F["PDF Export"]
+
+    style A fill:#4CAF50,stroke:#2E7D32,color:#fff
+    style E fill:#2196F3,stroke:#1565C0,color:#fff
+    style F fill:#FF9800,stroke:#F57C00,color:#fff
+```
+
+The CLI processes your markdown through multiple stages:
+1. **Parse** - Extract frontmatter and block directives
+2. **Transform** - Convert to widget tree
+3. **Render** - Flutter builds the UI
+4. **Export** - Generate PDF and thumbnails
+
+---
+
+@column {
+  flex: 2
+  align: center_left
+}
+### Getting Started {.heading}
+
+@column {
+  flex: 3
+}
+
+#### Installation
+
+```bash
+# Add to your Flutter project
+flutter pub add superdeck
+
+# Create your slides
+touch slides.md
+
+# Build and watch
+dart run superdeck_cli:main watch
+```
+
+#### Run
+
+```bash
+flutter run -d macos  # or chrome, windows, linux
+```
+
+---
+
+## Styling System {.heading}
+
+@section {
+  flex: 3
+}
+
+@column {
+  flex: 1
+}
+
+#### Global Themes
+
+Define in `superdeck.yaml`:
+
+```yaml
+styles:
+  default:
+    background: '#1a1a2e'
+    primaryColor: '#4CAF50'
+```
+
+@column {
+  flex: 1
+}
+
+#### Per-Slide Styles
+
+Apply via frontmatter:
+
+```markdown
+---
+style: quote
+---
+
+> Your quote here
+```
+
+---
+
+## Advanced Features {.heading}
+
+@column
+
+- **Mermaid Diagrams** - Flowcharts, sequences, mind maps
+- **Code Highlighting** - Syntax-aware formatting
+- **Custom Widgets** - Embed any Flutter widget
+- **PDF Export** - Print-ready output
+- **Thumbnails** - Auto-generated previews
+- **Responsive** - Adapts to any screen size
+
+---
+
+@section {
+  flex: 2
+}
+@column {
+  align: center
+}
+## "The best presentation tool is the one that gets out of your way." {.heading}
+
+##### Focus on content, not formatting {.subheading}
+
+---
+
+@section {
+  flex: 2
+  align: bottom_center
+}
+# Start Building {.heading}
+## github.com/leoafarias/superdeck {.subheading}
+
+@section
+
+@column {
+  align: center
+}
+MIT License | Flutter & Dart
+

packages/core/lib/src/models/block_model.dart

@@ -144,14 +144,11 @@ class SectionBlock extends Block {
   }
 
   /// Validation schema for section blocks.
-  ///
-  /// Note: 'blocks' is required (not optional) to satisfy Google AI schema
-  /// requirements which reject OBJECT types with all-optional properties.
   static final schema = Ack.object({
     'align': ContentAlignment.schema.optional(),
     'flex': Ack.integer().optional(),
     'scrollable': Ack.boolean().optional(),
-    'blocks': Ack.list(Block.discriminatedSchema),
+    'blocks': Ack.list(Block.discriminatedSchema).optional(),
   }, additionalProperties: true);
 
   @override
@@ -234,14 +231,11 @@ class ContentBlock extends Block {
   }
 
   /// Validation schema for content blocks.
-  ///
-  /// Note: 'content' is required (not optional) to satisfy Google AI schema
-  /// requirements which reject OBJECT types with all-optional properties.
   static final schema = Ack.object({
     'align': ContentAlignment.schema.optional(),
     'flex': Ack.integer().optional(),
     'scrollable': Ack.boolean().optional(),
-    'content': Ack.string(),
+    'content': Ack.string().optional(),
   }, additionalProperties: true);
 
   @override

packages/superdeck/lib/src/export/async_thumbnail.dart

@@ -39,6 +39,8 @@ class AsyncThumbnail {
     _status.value = AsyncFileStatus.loading;
     final currentFile = _imageFile.value;
     if (currentFile != null) {
+      // Clear all cached images to ensure stale thumbnails don't linger
+      imageCache.clear();
       FileImage(currentFile).evict();
     }
     _imageFile.value = null;
@@ -123,7 +125,7 @@ class AsyncThumbnail {
     }
 
     return Image(
-      gaplessPlayback: true,
+      gaplessPlayback: false,
       image: provider,
       errorBuilder: (context, error, _) => _errorWidget(context, this),
     );