D288 - Environment variables are named from one registry

Status: decided Date: 2026-08-26

Every crate names an environment variable through orbistoun_env::<VAR>.name. A trial clears every variable of Kind::Diagnostic before it runs and leaves settings alone.

Why: a second hand-written list drifts silently; a new diagnostic missing from it leaks into every trial of a sweep that claims to be controlled. Settings such as the data directory are how a trial is pointed at its own trace directory, so clearing them would send runs at the machine's real one. Literals remain only where option_env! needs one or a test asserts the spelling on purpose.

Rejected:

• A per-crate list of diagnostics to clear: already missed one variable when it was replaced.
• Clearing every registered variable: discards the settings a trial depends on.