Revise preprint prose and reorganize introduction

- Remove comparison table; reframe as collaborative positioning
- Fix Berther/Banellis chronology, soften tone on own team's work
- Reorganize intro: physiology → clinical+broader interest →
  gastric-brain science (conceptual grouping) → methods+software gap
  → GastroPy
- Tighten abstract: collapse feature list, cut API details and
  boilerplate outline sentence
- Prose edit throughout: remove dead rhetoric, hollow emphasis,
  template structures, over-hedging (prose-editor agent)
- Solo author for preprint
- Version PDFs: v1 (pre-prose-edit), v2 (current)

Author: micahgallen