By: syd <syd@kronor.io>
Make test derivation outputs deterministic nix build --rebuild reported the test derivations as possibly non-reproducible: their output was Vitest stdout verbatim, which carries a wall-clock start time and per-file durations. That defeats --rebuild and would defeat any content-addressed early cutoff, since a rerun of unchanged tests produced a different output hash every time. The output is now a normalized summary: which files ran, how many assertions passed, and the totals, with the timing dropped. All nineteen per-package test derivations now pass --rebuild. The machinery the two prototypes share moves to nix/support.nix.