Each step is a SteamPipe build of Half-Life: when it shipped and which cvars and commands changed since the build before it.
Changes tagged engine also show up in valve_WON (its game DLLs never change), so they come from hw.dll; the rest from the Half-Life DLLs.
Speedrun packs aren't releases: each one is assembled from files of several releases. Every pack below
lists where its core files come from, and how its valve dump differs from the same engine build on Steam.