cmd/sgai: keep live workspace detail tabs responsive under load

[ucirello]

Summary

• split workspace detail refresh into per-surface API endpoints and revision tokens so SSE-driven state updates only refetch the active tab instead of reloading every detail payload
• cache workspace detail subscriptions with useSyncExternalStore and keep event, message, and log tabs on bounded tail windows so live churn preserves focus and avoids runaway rendering
• add Go, React, and Playwright high-load coverage around selective revisions, stable tail rendering, and editor usability while unrelated updates continue streaming, and absorb the updated browser-bug-testing workflow into cmd/sgai/skel/.sgai

[ucirello]

https://github.com/ucirello/sgai/actions/runs/23621220941 - both checks are failing

[ucirello]

I checked the failing run at https://github.com/ucirello/sgai/actions/runs/23621220941. Both jobs are red because make test fails in the React suite; the actionable failure is the Dashboard test that times out waiting for [data-testid="redirect-target"] in cmd/sgai/webapp/src/pages/__tests__/Dashboard.test.tsx:922. I am keeping the PR in draft; no PR metadata changes looked necessary beyond recording the current state.