Fix typos in paper and docs and run spell check pass

[theo-barfoot]

Context

Raised during JOSS review (openjournals/joss-reviews#10072) by @yewentao256.

Problem

Reviewer flagged the typo "distringuishing" (should be "distinguishing") and recommended checking for other typos.

Typo "distringuishing", please check if there are other typos.

Required Changes

• Fix "distringuishing" → "distinguishing" (locate in paper, docs, or code docstrings)
• Run a spell check pass across paper/paper.md, README.md, and RST docs in docs/source/
• Fix any other typos found