refactor: remove local filesystem workspace system and replace with demo data

This commit removes the entire filesystem-access based workspace system:
1. Deletes workspace types and file system access store modules
2. Removes filesystem-related logic from App component and sidebar/nav components
3. Replaces dynamic workspace handling with hardcoded demo project data
4. Simplifies the UI to show placeholder dashboard content instead of project editor

Author: Sayhi-bzb

.agents/skills/agent-html/references/examples.md

@@ -11,6 +11,7 @@ Use the closest valid fixture before inventing new structure.
 ## Valid Patterns
 
 - `card-tabs-grid.xml`
+- `codeblock-basic.xml`
 - `complex-dashboard.xml`
 - `icon-basic.xml`
 - `image-basic.xml`
@@ -24,6 +25,9 @@ Use the closest valid fixture before inventing new structure.
 - `bare-text-under-section.xml`
 - `carousel-missing-content.xml`
 - `chart-missing-series.xml`
+- `codeblock-empty.xml`
+- `codeblock-invalid-language.xml`
+- `codeblock-missing-language.xml`
 - `image-invalid-fit.xml`
 - `image-invalid-src.xml`
 - `image-with-child.xml`

.agents/skills/agent-html/references/grammar.md

@@ -86,6 +86,8 @@
 - `ChartSeries:key=string, label?=string`
 - `ChartTooltip:hideLabel?="true|false" -> none`
 
+- `CodeBlock:language="ahtml|html|tsx|jsx|ts|js|json|bash", title?=string -> raw code text`
+
 - `Icon:name=string -> none`
 - `Image:src=string, alt=string, fit?="cover|contain" -> none`
 - `Text:variant?="h1|h2|h3|h4|p|lead|large|small|muted|inline-code" -> Text`
@@ -97,6 +99,11 @@
   <Section width="reader">
     <Stack>
       <Text variant="muted">Use Text for standalone copy inside layout nodes.</Text>
+      <CodeBlock language="tsx" title="Example.tsx">
+function Example() {
+  return <div>Hello</div>
+}
+      </CodeBlock>
     </Stack>
   </Section>