Fix POWER formula returning the base for a zero exponent

[Osamaali313]

Problem

The POWER(base, exponent) formula function (packages/core/src/formula/functions/numeric.ts) reads its exponent with a truthy fallback:

eval(params: TypedValue<number | null>[]): number | null {
  const value = params[0].value;
  if (value == null) return null;
  const exponent = params[1]?.value || 1;
  return Math.pow(value, exponent);
}

POWER(x, 0) must return 1 (the identity x⁰ = 1), but 0 || 1 evaluates to 1, so the exponent silently becomes 1 and the function returns the base x instead of 1.

validateParams throws when fewer than 2 params are supplied, so params[1] always exists at eval time — the || 1 "default" is never needed for a missing argument, and its only reachable effect is corrupting an explicitly-passed 0.

Evidence (siblings prove intent)

Ceiling and Floor in the same file use params[1]?.value || 0 — harmless because their default (0) equals the falsy value. Power is the one case where the default (1) differs from the meaningful falsy input (0), so || 1 can only ever misfire.

Reproduction

formula	expected	before	after
POWER(2, 0)	1	2 ❌	1 ✅
POWER(10, 0)	1	10 ❌	1 ✅
POWER(2, 3)	8	8	8

Fix

const exponent = params[1]?.value ?? 1;

?? preserves the null-safety intent while honoring an explicit 0. Existing tests (numeric.spec.ts) only cover exponents 2 and -2, so the zero case was unguarded.

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