docs: published manual edit links point to nonexistent dev branch

[Labeeb2339]

Problem

manual/source/conf.py configures Furo source edit links as:

html_theme_options = {
    "source_edit_link": "https://github.com/hedge-dev/HedgehogEngineBlenderIO/edit/dev/manual/source/{filename}",
}

The repository currently exposes only main and gh-pages branches; there is no dev branch. As a result, the Edit this page links in the published manual point to GitHub 404 pages.

Suggested fix

Point the link at the branch that actually contains the documentation source (currently main), or restore/update the intended branch if the site is generated from another ref. It would also be useful to verify one generated page after the change.

Evidence

• File: manual/source/conf.py
• Branches checked through the GitHub repository API: main, gh-pages