docs: add missing assistant.usage event fields to streaming-events re… #1870

Job	Run time
Rust SDK Bundled CLI Build (ubuntu-latest)	3m 18s
Rust SDK Tests (macos-latest, inprocess)	12m 56s
Rust SDK Tests (ubuntu-latest, default)	10m 22s
Rust SDK Tests (windows-latest, default)	12m 35s
Rust SDK Tests (macos-latest, default)	8m 25s
Rust SDK Tests (ubuntu-latest, inprocess)	15m 12s
Rust SDK Bundled CLI Build (macos-latest)	2m 25s
Rust SDK Bundled CLI Build (windows-latest)	4m 32s
	1h 9m 45s

Navigation Menu