rust-source-of-truth.md: add the "two-path divergence" rule to the canonical
content store section. Content reaches the sim two ways — in-game (GDScript
DataLoader reads JSON at runtime, projection.rs:41) and headless (Rust falls back
to a compile-time include_str!/hardcode copy, dispatch.rs:410). A balance constant
hardcoded in a crate is both a Rail-2 violation and a silent second copy that
drifts from the JSON — and headless is where the AI trains. Rule: grep
public/resources + public/games/**/data for a JSON home before adding a numeric
balance const; if it exists, LOAD it (OnceLock+include_str!, never std::fs in
shared sim code). References the p3-28 ContentRegistry endgame.
p3-28: add the matching "Rail-2 verify gate (enforcement)" acceptance bullet —
tools/check-no-rust-hardcoded-content.py + a verify step to catch the next
hardcode, best landed alongside the ContentRegistry.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>