Visual compare can screenshot before local stylesheets finish loading

[chubes4]

Problem

wordpress.visual-compare can produce and classify a pixel diff while local linked stylesheets are still pending. waitForVisualComparePaintReady() caps its load wait and stylesheet wait at 10 seconds each, even when the command has a substantially larger wall timeout. Capture diagnostics then report pending stylesheets and low-confidence readiness, but the already-written screenshots continue into comparison as if they were conclusive.

This can create a false large layout delta when a pending stylesheet owns responsive visibility or geometry.

Expected behavior

• Use a bounded stylesheet-readiness budget derived from the visual command timeout.
• Preserve enough wall time for settling, snapshots, screenshots, and diagnostics.
• Do not classify screenshots as conclusive visual evidence when required local stylesheets remain incomplete.
• Cover delayed local stylesheet loading with deterministic tests.

Acceptance criteria

1. A local stylesheet that completes within the derived readiness budget is applied before capture.
2. A stylesheet that remains pending after the budget produces explicit incomplete-capture evidence rather than a misleading visual-diff classification.
3. Existing external-request isolation and overall command bounds remain intact.

AI assistance

OpenAI GPT-5.6 Sol via OpenCode diagnosed the capture evidence, traced the owning implementation, and drafted this issue under human direction.