Module param_text 

2026-09-26: Text ↔ ParamValues: the conversions a run record (history.rs) and a --param flag need.

A stored run describes its whole configuration as text. Text goes back through crate::params::ParamKind::parse, the domain check the edit box uses, so an old value that is no longer legal is reported, not accepted.

Owner: bench (parameters). Invariants:

• ParamValues::from_overrides refuses an unknown key and an out-of-domain value; it never returns a partial set.