Fix activity center file action alignment

[zzj3720]

Summary

• Move Accept/Reject file review actions into the activity center title group so they sit immediately beside Workspace file changes.
• In file-review mode, hide the task/status icon and avoid duplicating the conversation/task title; the row is just the file changes heading plus review actions.
• Keep cancel/expand controls in the trailing control group.
• Add jsdom component tests that lock the action order/grouping and prevent title duplication.

Validation

• cd web && yarn test activity-center.test.tsx
• cd web && yarn typecheck
• cd web && yarn lint
• cd web && yarn build:embedded (passes with existing asset-size warnings)
• minimachine: cd web && yarn test activity-center.test.tsx
• minimachine: cd web && yarn build:embedded (passes with existing asset-size warnings)
• minimachine: cd macos && SWIFTFORMAT_VERSION=0.60.1 BUILD_CONFIGURATION=UnsignedDebug bash DevKit/Scripts/workspace_build_debug.sh (passes; existing SwiftLint/deprecation warnings only)
• Manual: launched the macOS app on minimachine and captured the task panel via VNC with a temporary dev fixture; screenshot posted in the Slack thread.

Note: Slack requester has no GitHub binding in the broker, so no requester author/co-author trailer was added.

[zzj3720]

Closing: this Slack thread target was corrected to cueboard, not OpenBridge.