Adds `agents.defaults.skipOptionalBootstrapFiles` for optional workspace bootstrap files, validates the supported filenames, and propagates the option through workspace bootstrap callers.
Also preserves legacy setup detection when `USER.md` or `IDENTITY.md` are intentionally skipped, documents the config field, and includes focused regression coverage.
Landing follow-up included small CI unblockers for current-base drift: removing an unused Brave runtime dependency, fixing Telegram RTT lint, and preserving compatible gateway-bindable plugin registry cache reuse when runtime ensures disable bundled dependency installation.
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