This is a wonderfully elegant use of Service Workers. Intercepting the request at the browser level to do instant local routing instead of waiting for a round-trip to the search provider is one of those 'why didn't I think of that' hacks.
Quick question on the implementation: How are you managing the storage and lookup for the 14,000+ bangs? Are they just bundled as a static JSON in the SW payload, and does that have any noticeable impact on the browser's memory footprint when the Service Worker activates?
Quick question on the implementation: How are you managing the storage and lookup for the 14,000+ bangs? Are they just bundled as a static JSON in the SW payload, and does that have any noticeable impact on the browser's memory footprint when the Service Worker activates?