chore: move documentation dependencies into their own group

[badja-dev]

What type of PR is this?

• Bug Fix (non-breaking change which fixes an issue)
• Feature/Tweak (non-breaking change which adds new functionality or enhances existing functionality)
• Breaking Change (fix or feature that would break any existing functionality for users)
• Documentation Update
• Chore (maintenance, dependency bumps, housekeeping - no functional change)
• Other

Description

[project].dependencies declared 42 packages, 17 of which are the mkdocs documentation toolchain. Stack 4 of 5, based on #3555.

None of those 17 are imported anywhere in modules/ or kometa.py. They exist only to build the documentation site. This moves them into a docs dependency group. docs is not a default group, so uv sync no longer pulls the documentation stack into a runtime environment.

After the split, [project].dependencies and requirements.txt agree exactly:

[project].dependencies: 25    requirements.txt: 25
in pyproject only: none
in requirements only: none
version specifier mismatches: none

Two lists that have been maintained by hand in separate files now match package for package and specifier for specifier.

docs/requirements.txt is unchanged, so the Read the Docs build is unaffected.

This is a prerequisite for #3557, which generates requirements.txt from the lockfile. Without the split, the generated file would pull the entire documentation stack into every image.

No CHANGELOG entry: no user-facing change.

Have you updated the Documentation to reflect changes (if necessary)?

• Yes
• No
• Not Applicable

Have you updated the JSON Schema files (if necessary)?

• Yes
• No
• Not Applicable

Have you updated the CHANGELOG.md?

• Yes
• No

[chazlarson]

LGTM