[danmar]

Extend the GUI help with detailed explanations and new screenshots:

• rewrite the existing pages and describe every option in the project file dialog and the preferences
• add pages for the main window, suppressions, results files/printing/ statistics, scratchpad/library editor, command line options and troubleshooting
• add a shared stylesheet, a contents tree and index keywords
• replace the old screenshots with new ones of the current GUI
• remove the obsolete manual.html (Cppcheck 1.46)

[dmcppcheck]

AI review

This PR only changes documentation. I found one factual error, in tools.html: it says scratchpad code "can not include your own headers". That is wrong. The scratchpad analyzes the code with the include paths of the open project, so #include "myheader.h" works for headers in those folders.

Nothing else I checked was wrong:

• Every link, anchor and image in the HTML pages and in online-help.qhp resolves.
• online-help.qhp lists every file in gui/help, and nothing still refers to the deleted manual.html or the old screenshots.
• These parts match the GUI source:
  • the command line options;
  • the startup behaviour;
  • the keyboard shortcuts and menu names;
  • the default build dir name;
  • which fields are disabled after an import;
  • the import file types;
  • the default file name in the scratchpad;
  • the message about addons needing a build directory.

Testing

• Build and tests: I did not build cppcheck or testrunner, and I ran no tests. The PR touches only gui/help (HTML, CSS, PNG and the .qhp file), so no C++ code or test changes. The GUI and qhelpgenerator are not available here, so I could not generate the help collection or view it.

• Links and files: I wrote a small Python checker (scratch/chk.py, run with python3 -I chk.py /work/pr/gui/help). For every href and src in the help pages and every ref in online-help.qhp, it checks that the target file and the <a name=...> anchor exist. It also checks that every HTML, PNG and CSS file is listed in <files> and that every listed file exists. It printed no problems. The "Previous" / "Next" links form one consistent chain.

• Text against the source: I compared what the help says with the GUI code. Sources checked:

  • gui/main.cpp and MainWindow::handleCLIParams (-p, -l, -d, .cppcheck and .xml arguments);
  • MainWindow::loadSettings (reopening the last project only when there are no arguments);
  • the shortcuts and menu texts in mainwindow.ui;
  • the build dir name at mainwindow.cpp:2069;
  • ProjectFileDialog::updatePathsAndDefines and the import filters;
  • ResultsTree::keyPressEvent (Enter opens the editor);
  • ScratchPad::checkButtonClicked (empty name means test.cpp).

  Everything matched except the scratchpad remark about headers. MainWindow::analyzeCode calls getCppcheckSettings, which adds the project's include folders to the settings (addIncludeDirs at mainwindow.cpp:1140), and then calls checkBuffer with those settings, so headers in the project's include folders are found.

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Automated review of 715fe3c by Claude. The pull request was built and tested locally.