Fix review findings in the regex engine, search count and journal v2

- PCRE2: compile with the ANYCRLF newline convention and DOLLAR_ENDONLY,
  as ECMAScript reads '.' and '$'. With PCRE2's default (LF only) '.'
  matched the CR of a CRLF line, so regex replace-all deleted CRs.
- Replacement $0 is the whole match, two digits are read greedily and a
  group the pattern lacks expands to nothing, as std::regex_replace
  (libstdc++) does; these cases are now compared in the tests.
- Plain search visits overlapping matches going forward too, and counts
  them, as the backward search found them ('aa' in 'aaa' read 2/1).
- The recovery prompt's replayed content is used on 'y' only if the
  journal is unchanged since; otherwise it is replayed again.
- A version 1 journal continued after recovery is rewritten as a
  compacted version 2 journal when it needs a chunked checkpoint,
  instead of receiving records an older kte would skip. (The version is
  read through a separate descriptor: the journal fd is write-only.)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015rcVQiiWyTzoNrsvLSaAfB

Command.cc

@@ -1169,7 +1169,7 @@ search_count(const Buffer &buf, bool regex, const std::string &q, const RegexMat
 			else
 				c.reached = true;
 			++c.total;
-			p += q.size();
+			p += 1; // overlapping, as Next/Previous visit them
 		}
 		if (p != std::string_view::npos && p >= cur_off)
 			c.reached = true;
@@ -1238,7 +1238,9 @@ run_search(Editor &ed, Buffer &buf, bool regex, SearchStep step, bool incrementa
 		x = ed.SearchOrigX();
 	}
 	if (step == SearchStep::Next && have_cur) {
-		const std::size_t len = std::max<std::size_t>(ed.SearchMatchLen(), 1);
+		// Plain search visits overlapping matches ("aa" in "aaa" at 0 and 1),
+		// as the backward search does; a regex continues after its match.
+		const std::size_t len = regex ? std::max<std::size_t>(ed.SearchMatchLen(), 1) : 1;
 		x += len;
 		if (x > line_text_view(buf, y).size() && y + 1 < buf.Nrows()) {
 			++y;