move handler methods into ParserMode classes and rename Handler

Each ParserMode class now implements handle() from ModeInterface,
containing the token handling logic that previously lived as individ

move handler methods into ParserMode classes and rename Handler

Each ParserMode class now implements handle() from ModeInterface,
containing the token handling logic that previously lived as individual
methods on Doku_Handler.

The Handler class (formerly Doku_Handler) is the single dispatch point:
Lexer passes tokens to Handler::handleToken() which routes to mode
objects, plugins, or returns false. The Lexer only tokenizes and
resolves mapHandler aliases.

Key changes:
- Add handle() to ModeInterface, implemented by all mode classes
- Move Doku_Handler to dokuwiki\Parsing\Handler namespace
- File extends Code (shared parsing via $type property)
- Quotes uses mapHandler() + Handler::getModeName() for sub-modes
- Media::parseMedia() replaces Doku_Handler_Parse_Media()
- Code::parseHighlightOptions() replaces parse_highlight_options()
- Per-parse state (footnote, doublequote) stays on Handler
- Deprecated wrappers kept for base/header/internallink/media
- Class alias and rector rules added for backward compatibility

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split Formatting into individual classes per formatting type

Introduce AbstractFormatting as a base class and seven concrete
classes (Strong, Emphasis, Underline, Monospace, Subscript,
Superscript,

split Formatting into individual classes per formatting type

Introduce AbstractFormatting as a base class and seven concrete
classes (Strong, Emphasis, Underline, Monospace, Subscript,
Superscript, Deleted) that each define their own patterns and
sort order. Delete the old Formatting class and update tests
to use the new classes directly. ModeRegistry now treats
formatting modes as regular built-in modes.

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