Complete and refresh XRLint documentation

[forman]

Description:

The documentation contained unfinished configuration sections and outdated descriptions of plugin discovery, rule names, and API behavior.

This PR completes every “Coming soon” section, refreshes the CLI/API and contributor guides, and adds runnable examples. The generated rule reference now includes qualified identifiers, preset names, and option schemas. It also documents existing ACDD preset limitations and a working strict-recommended override.

Includes corrected source docstrings and CLI help, a changelog entry, and the version update to 0.7.0.dev0.

Checklist (strike out non-applicable):

• Changes documented in CHANGES.md
• Related issue exists and is referred to in the PR description and CHANGES.md
• Added docstrings and API docs for any new/modified user-facing classes and functions
• Changes/features documented in docs/*
• Unit-tests adapted/added for changes/features
• Test coverage remains or increases (target 100%)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.42%. Comparing base (b420ac8) to head (36843ff).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #77   +/-   ##
=======================================
  Coverage   99.42%   99.42%           
=======================================
  Files          75       75           
  Lines        2975     2975           
  Branches      432      432           
=======================================
  Hits         2958     2958           
  Misses          1        1           
  Partials       16       16           

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