Durable idris2 (+ zig) toolchain for web sessions

[hyperpolymath]

Relegated from the thread. Web-session containers ship without idris2 / pack / zig, so the proof loop is CI-only unless reinstalled per session.

Confirmed working install path (this session): chezscheme is preinstalled; a from-source idris2 0.8.0 bootstrap (make bootstrap SCHEME=chezscheme && make install) takes ~5–8 min and then idris2 --build ochrance.ipkg + all suites pass locally. zig is blocked — ziglang.org is not on the network allowlist (403); a mirror or allowlist entry is needed for the FFI build+test locally.

Make it durable so every session has a fast local proof loop:

• SessionStart hook / environment setup script that installs idris2 0.8.0 (+ zig once reachable), or
• a prebaked environment image with the toolchain (preferred — avoids ~5–8 min per session start).
• allowlist ziglang.org (or vendor a zig mirror) for the FFI checks.

https://claude.ai/code/session_011z2t8zAxfcCNLJzU7YdpBQ