Enhancement (configuration): Add keepescape mode 4 to repair Pandoc escapes - #217

OneNote pages often start paragraphs with a literal - or 7. instead of using real lists. Pandoc escapes such text so it does not turn into a list (\- item, 7\. item). In an export of two notebooks (393 pages) this left the notes with plain paragraphs instead of lists, a blank line between every item, a literal \ at the end of many lines (Pandoc's hard line break) and many needless escapes (--\>, snake\_case).

The existing keepescape modes cannot fix this: 1 deletes every backslash (also in Windows paths such as C:\Program Files), 2 and 3 keep the list escapes.

This PR adds keepescape = 4, implemented as the function Repair-MarkdownEscapes, run on Pandoc's output before the existing replacements:

• Rebuilds lists from \- item and 7\. item (also inside block quotes and when a non-breaking space follows the marker), removes the blank lines between list items, and drops lone - lines (empty bullets, or an accidental heading underline).
• Turns a \ at the end of a line into two trailing spaces, or drops it at the end of a paragraph.
• Removes escapes that cannot change the rendering (\> in --\>, \_ in snake\_case, \. and \- in the middle of a line).
• Keeps escapes that matter: at the start of a line, \[, \], \* pairs, \, Windows and UNC paths.
• Never touches code fences and inline code.

The default (1) and modes 1 to 3 are unchanged. A literal - at the start of a line is treated as a list in mode 4; use 3 if that is not wanted.

Tested

• 22 new unit tests: each rule, cases that must stay untouched (Windows and UNC paths, \*, code), block quotes, non-breaking spaces, running it twice gives the same result, and that mode 4 adds no replacement that touches backslashes.
• Real run against OneNote with two notebooks (393 pages, same .docx files, mode 3 against mode 4): escaped bullets 601 to 0, blank lines between list items 67 to 0, line-end backslashes 1804 to 0, lone - lines 29 to 0, escaped numbers 133 to 0. The letters and digits of every page are identical in both modes, so no text is lost.
• Unit tests: 96 passed in Windows PowerShell 5.1; the one failure ("Throw if -Length is greater than 255") expects the English .NET error message and also fails on master on a German Windows.
• Not tested here: PowerShell 6.x and 7.0 (see CI: Remove the retired windows-2019 job and the unusable PowerShell 6.x/7.0 container jobs #216).

🤖 Generated with Claude Code