Replace the inferred exponential media progression with the four initialized
32-bit thresholds used by the original score-addition path: 140,000, 650,000,
1,300,000, and 4,000,000. Award exactly one media level and extra ball at each,
with no nonexistent fifth tier.
Test Plan:
- `cargo test --all-targets` -- 50 passed
- `cargo clippy --all-targets -- -D warnings` -- passed
- `cargo build --profile production` -- passed
- threshold boundary and four-extra-ball test -- passed
- `git diff --cached --check` -- passed
ddidderr
77c93ec36b