The docs evaluation referenced self.nixosConfigurations.agent-base and
self.nixosModules.default — both tied to self's full flake store path.
Every commit produces a new self hash (even when only Rust or frontend
files change), so docs drvs change on every commit and the remote
builder (muede-pc2) must rebuild them from scratch each time.
Fix: use builtins.path on the nix/ directory with
builtins.unsafeDiscardStringContext to produce a content-addressed store
path (nixSrc) that only changes when .nix files change. Evaluate both
hostEval and agentEval from nixSrc using stub package args (pkgs.emptyFile /
pkgs.emptyDirectory) instead of self.overlays.default, which avoids
pulling in the Rust and frontend build closures.
Now docs drvs only change when a .nix file changes. PRs that touch only
Rust or frontend code hit the remote builder cache instead of forcing a
rebuild. Closes the disk-pressure-induced CI failure loop on muede-pc2.
Forge URLs in transformOptions updated to prepend nix/ prefix correctly
(nixSrc is a copy of nix/, so stripped paths need nix/ re-added).