Adds the Omnigent SVG icon to the built-in site icon assets so modules
and templates can reference `/icon/omnigent.svg`.
## Validation
- `./scripts/check_site_icons.sh`
- Verified `site/src/theme/icons.json` is sorted and includes
`omnigent.svg`
- Parsed `site/static/icon/omnigent.svg` as valid XML
> 🤖 This PR was created with the help of Coder Agents, and needs a human
review. 🧑💻
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Co-authored-by: Jake Howell <jake@hwll.me>