GfmEscape: defer \\<EOL> to DW Linebreak in mixed-syntax modes

Both GfmEscape (sort 5) and DW Linebreak (sort 140) can claim the
two backslashes of `\\` followed by space/tab/newline. The lexer's
ti

GfmEscape: defer \\<EOL> to DW Linebreak in mixed-syntax modes

Both GfmEscape (sort 5) and DW Linebreak (sort 140) can claim the
two backslashes of `\\` followed by space/tab/newline. The lexer's
tie-breaker picked GfmEscape, so DW's forced linebreak silently lost
its delimiter under dw+md and md+dw. Add a negative lookahead that
declines `\\[ \t\n]` whenever DW syntax is loaded — pure md keeps
GFM-spec behavior. Mid-line `\\` (UNC paths etc.) still escapes.

show more ...

GFM modes: follow CATEGORY_SUBSTITION → CATEGORY_SUBSTITUTION rename

Constant was renamed on master (the typo'd 'substition' value is kept,
but the constant name spells it correctly). Update GfmTabl

GFM modes: follow CATEGORY_SUBSTITION → CATEGORY_SUBSTITUTION rename

Constant was renamed on master (the typo'd 'substition' value is kept,
but the constant name spells it correctly). Update GfmTable's use of
the constant, plus stale docblock/comment references in GfmEscape,
GfmHtmlEntity, GfmLinebreak, and GfmLinebreakTest.

show more ...

add GfmLinebreak for GFM hard line breaks

Two-or-more trailing spaces, or a single backslash, immediately before
a non-final newline render as a `<br/>`. Both delimiter forms share a
single SUBSTITI

add GfmLinebreak for GFM hard line breaks

Two-or-more trailing spaces, or a single backslash, immediately before
a non-final newline render as a `<br/>`. Both delimiter forms share a
single SUBSTITION mode at sort 140, loaded under any MD-active syntax
(markdown, dw+md, md+dw); pure dokuwiki is unaffected.

Reuses the existing `linebreak` handler call and renderer; no new
instructions or renderer changes. SpecCompatRenderer overrides
linebreak() to emit the spec's `<br />` shape. Examples 662, 663
(line break inside a raw HTML tag) are skipped — raw HTML is not
passed through by default.

show more ...