Run the sequential Electron E2E suite as three Playwright shards per OS
(one runner each) and summarize all shards of an OS in one follow-up job.
The semantic summary script accepts a directory of shard reports, merges
them and refuses to write when a shard is missing, duplicated or
malformed, or when an explicit input does not exist.
Slowest shard per OS in the final run: ubuntu 12.5 min (was 26),
macOS 13.7 min (was 34), Windows 24.5 min (was 35).
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>