[codex-pony]

Fix Markdown copying when a PDF text selection ends at a sentence's punctuation but stops before the immediately following raised footnote marker. In the Securities Transfer Association's August 4, 2009 petition, PDF page 14 (printed page 13) displays note 25 after “self-regulatory organizations.”, while the enhanced text layer extracts the raised marker as 2s. The citation and its recovered note definition can therefore be omitted from the copied passage.

• Extend superscript detection to short elevated text runs containing s or S, and normalize those characters to 5 when matching an indexed footnote number. This affects citation recognition, not general OCR text.
• In selectionToMarkdown, include an otherwise unselected superscript when it immediately follows a fully selected span in text-layer order on the same page, only when Markdown copying is enabled and the marker is outside indexed footnote regions. Preserve native copying for untagged plain-text selections.
• Add an enhanced text-layer fixture for petition PDF page 14 and a regression case covering two selection endpoints. Check that organizations.²⁵ is followed by the recovered [25]: Allowing DTC… definition, which ends with same functions as transfer agents., without leaking 2s or creating an incorrect [5]: note. Also check Markdown-disabled behavior.

This extends the indexed-note recovery introduced in #183 and the Unicode-superscript, paragraph-adjacent footnote output refined in #187. It complements the terminal-punctuation drag-selection fix in #188 by handling the following citation marker during Markdown serialization instead of changing the drag endpoint.