v1.2.5

Fix backslash-escaped checklist brackets and punctuation not rendering

Text pasted from elsewhere sometimes defensively escapes markdown chars
(e.g. `- \[ \] todo`, `\~10`). The task regex only matched literal
brackets, so escaped checkboxes fell through to a plain bullet showing
raw `\[ \]` text; nothing unescaped punctuation elsewhere either. Adds
a CommonMark-aligned unescape pass used by both the plain-text preview
and the inline renderer.

Co-Authored-By: Claude <noreply@anthropic.com>