Add option to apply word wrap per document - #18488

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Adds the option "Word wrap applies to the current document only" to Preferences > Editing 1 (unchecked by default). When it is checked:

• View > Word wrap and its toolbar button wrap or unwrap the current document only (in both views if it is cloned), and the menu check, the toolbar button and the document map follow the current document;
• each document keeps its own word wrap in its Buffer, saved in session.xml like RTL (<File ... wordWrap="yes|no">). Documents without their own setting follow the global word wrap (Wrap in config.xml), which the command does not change while the option is on;
• the word wrap is set in ScintillaEditView::activateBuffer() before the position of the document is restored, so the first visible line is kept;
• with "Deactivate Word Wrap globally" (large file restriction), only the large file is unwrapped instead of all the documents;
• switching the option on or off takes effect immediately (new internal message NPPM_INTERNAL_WORDWRAPPERDOCUMENT).

About performance (mentioned in the issue): the word wrap of a document is set right after SCI_SETDOCPOINTER, and Editor::SetDocPointer() already calls NeedWrapping() for the new document. SCI_SETWRAPMODE does nothing when the mode does not change; when it changes, it marks the document for re-wrapping (already needed at that point) and refreshes the view style, which does not depend on the document size. So switching tabs costs about the same as with the global word wrap on, and less for the documents that are not wrapped.

Tested on Windows 11 with a Release x64 build of this branch (0 warnings), with an automated GUI test (Win32 messages, separate settings folder):

• option off (default): View > Word wrap is global as before, no new attribute in session.xml;
• option on: wrap and unwrap per document; menu, toolbar and document map follow the current document; same first visible line when coming back to a wrapped document; a cloned document is wrapped in both views;
• restart: the documents get their word wrap back from session.xml in both views (also the ones already shown while the session is loaded), at the same first visible line; documents without their own setting follow the global word wrap;
• option switched off: both views follow the global word wrap again; the own setting of the documents is kept in session.xml for when the option is switched on again;
• large file restriction with "Deactivate Word Wrap globally": only the large file is unwrapped, the global setting does not change.

The issue also suggests an entry in the tab context menu: it could be added on top of this, if wanted.

AI disclosure: the code and this description were written with Claude Code (Claude Opus 5.5); the build and the tests above were run on a real Windows 11 machine.

fix #5232

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