[BUG] Stabilize flaky accessibility contrast test after theme changes #1612

Type

Bug

Problem / Value

The accessibility contrast test can fail while theme colors are still transitioning. This creates false failures and reduces confidence in accessibility checks.

Failed job: https://github.com/Zoo-Code-Org/Zoo-Code/actions/runs/34611927505/job/103304287180?pr=1604

Reproduction evidence

• The failed check measured 3.73:1 against the required 4.5:1.
• Another run produced the same intermediate colors and failure.
• Five nearby runs passed.
• The final theme colors produce about 14.55:1 contrast.
• This is not a runner failure, accessibility regression, or PR 1604 regression.

Root cause

The theme helper changes theme classes without waiting for color transitions to finish. The input uses a 150 ms color transition, so the contrast helper can sample intermediate gray values.

Expected behavior

Contrast checks must measure stable final theme colors and produce consistent results across repeated runs.

Recommended approach

Disable transitions for this test, or wait for stable computed styles before measuring contrast.

Acceptance criteria

• The test does not measure colors during a theme transition.
• Repeated runs produce stable contrast results.
• The test still fails when final colors do not meet the required contrast ratio.
• The fix does not weaken the 4.5:1 requirement.