feat(preact+landing): enable Preact block rendering + reusable landing page content system

## Preact Block Integration
- Enable Preact component detection for data-driven pages:
  - Fix init.html to resolve sections_source + per-section ref before Preact detection
  - Correct resource paths: blox/* → js/hbx/blocks/* (Hugo module mounts)
  - Update libraries.html to load Preact core + compiled block scripts
- Add dynamic icon rendering for Preact components:
  - Create Icon.jsx component with SVG decoding
  - Add get_icon_data.html partial for passing icon strings to Preact props
  - Update preact-wrapper.html to fetch icon data and inject into props
  - Wire hero component to render dynamic icons via <Icon svg={icon_svg} />
- Centralized logging system:
  - Add functions/logger.html to wrap warnf/errorf safely
  - Degrade to HTML comments in constrained contexts (content adapters)

## Reusable Landing Page Content System
- Add sections_source support:
  - Page front matter: sections_source: pages/<key> loads base from data/pages/<key>.yaml
  - Inline sections deep-merge over base by position; extras appended
- Add per-section ref system:
  - Any section: ref: blocks/<slug> loads from data/blocks/<slug>.yaml
  - Inline section properties deep-merge over ref (content/design submaps)
  - Enable content reuse across multiple landing pages
- Create reusable block library:
  - Add test/data/blocks/: hero_basic.yaml, features_basic.yaml
  - Add test/content/linked/index.md demo using refs with overrides
- Add pragmatic deep merge for content/design override handling

## Infrastructure & Schemas
- Update base-block.json schema:
  - Fix gradient structure: flat → nested (gradient.start/end/direction)
  - Fix color structure: string|{light,dark} (matches parse_block_v3.html)
  - Update hero schema to properly extend base via $ref
- Fix Tailwind source path generation:
  - Add tailwind_sources.html with test vs starter site logic
  - scripts/view-test.sh: export HUGO_BLOX_TEST_SITE=true
- Update block directory structure:
  - blox/<name>/config.html (was blox/<name>--CONFIG.html)
  - Apply to init.html + parse_block_v2.html
- Code quality improvements:
  - Biome config: match Prettier rules

## Content Adapters (Removed)
- Investigated Hugo content adapters for landing pages
- Found execution context limitations (early build phase, limited site methods)
- Archived to backups/content-adapters-*.zip and removed from test site
- Decision: use standard pages + data linking instead of adapters

This enables dynamic Preact rendering with proper icon support while providing a flexible, reusable content system for landing pages that maintains the "single file = page" mental model with optional advanced linking.

vite.config.js

@@ -80,6 +80,21 @@ export default defineConfig({
           src: "node_modules/alpinejs/dist/cdn.min.js",
           dest: "alpinejs/",
         },
+
+        // Preact for interactive components
+        {
+          src: "node_modules/preact/dist/preact.min.js",
+          dest: "preact/",
+        },
+        {
+          src: "node_modules/preact/dist/preact.min.js.map",
+          dest: "preact/",
+        },
+        {
+          src: "node_modules/preact/hooks/dist/hooks.umd.js",
+          dest: "preact/",
+          rename: "hooks.min.js",
+        },
       ],
     }),