feat: implement session events, explore tools, and thread hierarchy #20

Job	Run time
test-js	2m 7s
typecheck	1m 2s
lint	59s
Rust tests (Windows)	13m 18s
Rust tests (macOS)	3m 50s
Rust tests (Linux)	11m 37s
Tauri build (${{ matrix.platform.name }})	-1s
	32m 52s

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