Developer mode already emitted useful workspace/session/perf logs, but they
mostly lived in the console and only a subset made it into exportable debug
artifacts. That made it hard to collect a clean report from users when chasing
racy workspace bugs.
Add a shared dev-log buffer, feed it from the existing app/workspace/session
and perf debug emitters, surface the log stream in Settings > Debug, and make
it copyable/exportable alongside the existing runtime debug report.
