Update the repository README.md and individual model README files.

## Steps

1. Find all `.scad` files in the repository using glob.
2. For each `.scad` file found:
   a. Read the `.scad` file to extract its name and description from the header comments (lines starting with `//` at the top of the file).
   b. Determine the model directory (the parent directory of the `.scad` file, relative to the repo root).
   c. Check if a `README.md` exists in that model directory. If not, create one with:
      - The model name as heading (from the first comment line)
      - The preview image (`![Preview](preview.png)`)
      - A description section (from the header comments)
      - A "Parameters" section listing the customizer parameters and their defaults extracted from the `.scad` file (variables with comments)
      - A "Print Notes" section if printing tips are found in comments
   d. If the model `README.md` already exists, update it to keep it in sync with the `.scad` file header.
3. Generate or update the root `README.md` with:
   - A heading: `# 3D Printing Models`
   - A brief intro line
   - A markdown table with columns: **Preview**, **Name**, **Description**
     - **Preview**: `<img src="{dir}/preview.png" width="200">` (use HTML img tag for sizing)
     - **Name**: linked to the model directory README: `[{name}]({dir}/)`
     - **Description**: short one-line description from the `.scad` header
   - Models sorted alphabetically by directory name