fix: correct O(N²) energy/FLOPs savings calculation (#95) (#97)

The energy_wh_saved and flops_saved values were orders of magnitude too
high because a scaling factor that grows linearly with N was applied to
the energy calculation, making it scale as O(N³) instead of O(N²).

Replace the buggy scale-factor approach with a direct FLOP-to-energy
conversion using each provider's per-token constants. Add regression
tests to prevent recurrence.

Closes #95

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/javascripts/leaderboard.js

@@ -10,6 +10,8 @@
   var currentPage = 0;
 
   // No-KV-cache formula: FLOPs = params_b * 1e9 * N * (N+1)
+  // Reference values only (GPT-5.3 constants) — recompute functions below
+  // are defined but not called; the leaderboard displays database values directly.
   var DEFAULT_PARAMS_B = 137;
   var ENERGY_WH_PER_FLOP = 0.4 / (1000 * 3e12);