test: enforce desktop visual and performance budgets

[kev1n77]

Summary

• add Playwright visual baselines for the minimum light and wide dark desktop workspaces
• enforce thousand-request bootstrap, scroll, filter, virtualization, and overflow budgets
• add a serialized fake-provider benchmark for Gateway capture P95 overhead
• publish browser reports in CI and update development progress evidence

Verification

• npm run desktop:check
• npm run desktop:build
• npm run desktop:e2e on Windows Chromium
• Playwright baseline comparison on Ubuntu 24.04 Chromium
• cargo test -p codeischeap-gateway --all-targets
• cargo test -p codeischeap-gateway --test performance -- --ignored --nocapture --test-threads=1
• cargo clippy -p codeischeap-gateway --all-targets -- -D warnings
• cargo fmt --all -- --check