[Yariminal]

At phone widths the session header expanded the page and clipped Home. A comparison opened at its footer, hiding the warning and previews, and stale keeper approval failures left an outdated proposal on screen. This fixes those observed browser defects.

• Keep the header, dashboard and review page within 320/390/768 px viewports, with navigation and tables scrolling inside their containers.
• Open long comparisons at their heading with contained keyboard navigation and restore focus on Escape.
• Show the server conflict reason and refresh the active session's review queue after a stale keeper rejection; discard late errors after a session switch.
• Expand the disposable UI fixture with two synthetic sessions and explicit provenance, and record acceptance evidence in docs/UI_ACCEPTANCE_2026-09-29.md.

Validation: browser checks on a separate merged-build fixture server covered desktop/phone/tablet layouts, actual keeper/candidate PNG previews, file provenance, Tab/Shift+Tab/Escape, read-only saved snapshots, and A-to-B count isolation. A real two-tab keeper change returned HTTP 409, never approved the stale candidate, and refreshed the queue to the new candidate. All six Node UI state checks and JavaScript syntax passed; targeted regressions cover the new conflict/focus behavior. The enhanced fixture generator was smoke-tested.

Follows the UI acceptance work in #7, independently of #8. Synthetic UI fixtures do not establish model-quality, consuming-app or physical 100–500 GB readiness. Controlled delayed-response races remain covered by Node tests. The existing live server on port 8765 could not be restarted because approval review blocked it; browser acceptance used isolated port 8766.