[vkbo]

Summary

This PR:

• Extracts the common parts of both headers and footers into base classes. This is a step towards the eventual merging of the editor and viewer into a single component.
• Adds a setting to hide most content of the document header when i Focus Mode. This is feature request Enhanced Focus Mode with Minimalist Interface #2225.
• Moves the Focus Mode toggle settings to the bottom of the Text Flow section.
• Redesigns the viewer footer into showing the Status/Importance label and the word count also for viewed documents, mirroring the editor layout.
• Moves the toggle buttons of the viewer footer into a pop-up menu on the left.
• Adds a "Enable First Line Indent" option to the viewer toggles. This is feature Allow first line indent in the viewer #3095.

Related Issue(s)

Closes #2225
Closes #3095

Submitter's Checklist

• I am familiar with, and have followed, the Contributing Guide
• I am familiar with, and have followed, the AI Policy

Reviewer's Checklist

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All linting checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed

[github-actions]

Coverage Report (Linux, macOS, Windows)

Name	Stmts	Miss	Branch	BrPart	Cover	Missing
TOTAL	28905	0	7092	0	100.000%

102 files skipped due to complete coverage.

Total: 100.000%