fix(parser): stop group-quantifier body patterns from exhausting memory

Several patterns repeat a group — (?:…)* / (?:…)+ — over a body that can
span a large region. On the non-JIT PCRE engine each

fix(parser): stop group-quantifier body patterns from exhausting memory

Several patterns repeat a group — (?:…)* / (?:…)+ — over a body that can
span a large region. On the non-JIT PCRE engine each iteration of a
group repetition keeps its own backtracking frame, so a big body retains
one frame per byte: a linear, unbounded memory spike that can fatal a
request (and, with JIT on, trips pcre.jit_stacklimit so the lexer dumps
the rest of the document as literal text). A repetition over a single
item (.* , [^x]+) is optimized by PCRE and unaffected.

Make each body possessive: the repeated group cannot match the delimiter
that follows it, so it always stops at the first closer and never needs
to backtrack.

- media {{…}}, windowssharelink, gfm_quote, gfm_link: possessive body.
- email validation (used by emaillink and mail_isvalid): possessive
local-part and domain groups; a long dotted `a.a.a…` local part or
domain was a ReDoS vector. Match results are unchanged.

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fix(parser): don't drop document content after a blank indented line

Preformatted's exit pattern (?=\n[^ \t\n]) is a lookahead-only exit: it
consumes no byte so the boundary \n stays in the stream f

fix(parser): don't drop document content after a blank indented line

Preformatted's exit pattern (?=\n[^ \t\n]) is a lookahead-only exit: it
consumes no byte so the boundary \n stays in the stream for a following block
mode (an <hr> or header after an indented code block) to anchor on.

When that exit fired with nothing else consumed - a "blank" line that is empty
after its indent, followed by a column-0 line - the match was zero-width at the
current offset and the lexer's no-advance guard aborted the whole parse,
silently discarding the rest of the document. Reachable on ordinary trailing
whitespace ("abc\n \nmore") and inside footnotes.

Exempt zero-width MODE_EXIT matches from the guard: popping the mode stack is
real progress and leaves the boundary byte for the parent mode to consume on
the next iteration. The stack strictly shrinks on each such exit, so this
cannot loop; the infinite-loop protection is unchanged for every other
zero-width match. Preformatted's pattern is left as-is, so <hr>/header after an
indented code block still works, including after a blank indented line.

Add regressions for the blank-line, blank-line-after-code, and
boundary-preservation (hr after a blank indented line) cases.

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Parsing: make parse syntax a per-parse value, drop ModeInterface

The active parse's syntax flavour is a per-parse question, not process-
global state: within a single request a plugin can render bun

Parsing: make parse syntax a per-parse value, drop ModeInterface

The active parse's syntax flavour is a per-parse question, not process-
global state: within a single request a plugin can render bundled
DokuWiki-syntax text inside an otherwise-Markdown page. Yet ModeRegistry
was a singleton that read $conf['syntax'] and the $PARSER_MODES global,
and every mode reached it through ModeRegistry::getInstance() — so the
flavour lived in shared mutable state that two parses in one request
would fight over.

Make the registry a short-lived value instead:

- ModeRegistry is constructed once per parse with an explicit $syntax
and injected into Parser, Handler and every mode. getSyntax() /
isDwPreferred() / isMdPreferred() consult $this->syntax; the
DOKU_UNITTEST-gated mode-list cache hack is gone (each registry is
fresh, nothing to invalidate).
- p_get_instructions() is now the single place in the pipeline where
$conf['syntax'] is read; from there the flavour travels as a
parameter. No code under inc/Parsing/ reads $conf['syntax'] directly
anymore — the five syntax-reading modes (Preformatted, GfmHr,
GfmEscape, Externallink, GfmQuote) route through $this->registry.

Keep the two concepts apart, as documented in the ModeRegistry and
AbstractMode docblocks: the user's configured *preference* stays in
$conf['syntax'] for UI code (toolbar, settings), while the active
parse's syntax is a parameter carried by the registry.

$PARSER_MODES is demoted to a deprecated, read-only mirror, published
during loadPluginModes() — third-party syntax plugins (columnlist,
alphalist2, phpwikify, skipentity) and the bundled info plugin read the
global directly, often from their constructors, so the taxonomy must
stay visible there. No core code reads the mirror.

Fold ModeInterface into AbstractMode while here: getSort()/handle() are
abstract, the connect callbacks carry defaults, and the public $Lexer
"FIXME should be done by setter" becomes setLexer()/getLexer() injected
by Parser::addMode() alongside the registry. Nested-content resolution
moves to the allowedCategories()/filterAllowedModes() hooks, resolved
once when the registry is attached.

Tests build their own parser/registry through ParserTestBase::setSyntax()
instead of mutating $conf and calling the removed ModeRegistry::reset().

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GfmQuote: accept ^> line starts so quotes can follow tables and lists

GfmTable, DW Table, and DW Listblock all consume the boundary \n on
their way out. A pure-lookahead exit pattern at that boundar

GfmQuote: accept ^> line starts so quotes can follow tables and lists

GfmTable, DW Table, and DW Listblock all consume the boundary \n on
their way out. A pure-lookahead exit pattern at that boundary would
trip the lexer's no-advance safety check, because tables and lists
exit right after consuming a marker token and have no leading
unmatched content for the lookahead to attach to (unlike Preformatted,
whose body leaves code lines as UNMATCHED right before the boundary).

Fix this on the consumer side: change the first-line anchor from \n>
to (?:^|\n)>. With the lexer's m flag, ^ matches at offset 0 and at
any position immediately following a \n in the subject, including the
position right after a \n that a preceding mode just consumed.
Subsequent quote lines keep the \n> anchor.

Adds three handoff tests in GfmQuoteTest covering GfmTable, DW Table,
and DW Listblock. Resolves GFM spec example 201.

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rename syntax flavors 'dokuwiki' / 'markdown' to 'dw' / 'md'

Symmetry with the existing 'dw+md' / 'md+dw' setting values.

replace DW Quote with unified GfmQuote

GfmQuote covers blockquote parsing for both DokuWiki and GFM dialects
in a single mode. Same quote_open/quote_close handler instructions; a
DW-preferred post-p

replace DW Quote with unified GfmQuote

GfmQuote covers blockquote parsing for both DokuWiki and GFM dialects
in a single mode. Same quote_open/quote_close handler instructions; a
DW-preferred post-pass flattens sub-parsed paragraph wrapping into
linebreak calls so existing pages keep their <br/>-between-lines
rendering. MD-preferred keeps the <p>-wrapped spec shape.

Block content (lists, fenced code, tables) inside `>` quotes now
renders, since the body is sub-parsed. Headers stay excluded
(BASEONLY) — TOC and section-edit anchors don't compose with
<blockquote>, same rationale as GfmListblock.

Convert ModeRegistry's sub-parser cache into an acquire/release pool
to support same-key re-entrancy: a list inside a quote re-enters
gfm_quote during the list-item sub-parse, and the inner call needs
its own parser instance even though the exclusion key matches.
GfmListblock is updated to use the new acquire/release primitives.

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