Add weeknotes system with first entry

- Add weeknotes landing page with auto-listing of all entries
- Create first weeknote: December 20–27, 2025
- Add Weeknotes to secondary menu alongside Now/Then/Future
- Create custom layout to display all weeknotes chronologically
- Update weeknotes command to use date ranges and current time
- Credit Genehack for weeknotes inspiration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.claude/commands/weeknotes.md

@@ -39,8 +39,8 @@ After gathering responses, create the weeknotes post:
 2. **Generate frontmatter**:
    ```yaml
    ---
-   title: "Weeknotes: [Date in 'January 2, 2006' format]"
-   date: [ISO 8601 datetime with -05:00 timezone]
+   title: "Weeknotes: [Start date]–[End date], [Year]" (e.g., "December 20–27, 2025")
+   date: [ISO 8601 datetime with -05:00 timezone, set to current time to avoid future-date issues]
    draft: false
    tags:
      - weeknotes
@@ -77,8 +77,8 @@ If he wants to preview, run `hugo server -D` in the blog directory.
 
 ```markdown
 ---
-title: "Weeknotes: December 27, 2025"
-date: 2025-12-27T12:00:00-05:00
+title: "Weeknotes: December 20–27, 2025"
+date: 2025-12-27T10:45:00-05:00
 draft: false
 tags:
   - weeknotes