Instrument and improve incremental workspace checks

Profile source capture, Nix evaluation/realization, resource/query checking,
and implementation builds without putting timings into immutable outputs.
Keep modular repositories; bound independent capture work, snapshot jj once
per observation, and retain final concurrent-edit and Git completeness checks.

Compose exact resource/closure/frontend/toolchain checks as memoized Nix
derivations. Preserve whole-workspace validation and the full compiler path
when no checked dependency is supplied. Share canonical Nixpkgs by content,
index workspace build contexts once, and narrow lock/driver/compiler inputs
with conservative complete-source fallback. Batch React witness checks only
when distinct source closures cannot share ambient declarations; otherwise
run the original independent TypeScript checks.

Seed local authoring toolchains with exact canonical fetch identities when
they match the selected inputs; retain store-path inputs for overrides.
Add generic correctness checks rather than permanent Reader timing/content
fixtures. Verify actual Reader edits and rejection/recovery in a private
workbench, preserving the original user's workbench and runtime.

Query checking currently caches at resource/closure boundaries, not individual
query semantic dependency boundaries. Template helper pins and reproducible
fixture snapshots follow in a separate publication change.

react-contracts.nix

@@ -6,6 +6,7 @@
   dependencies ? null,
 }:
 let
+  buildTools = import ./build-tools.nix;
   config = pkgs.writeText "camino-react-contracts.json" (
     builtins.toJSON {
       source = import ./implementation-source.nix {
@@ -33,5 +34,5 @@ let
   );
 in
 pkgs.runCommand "camino-react-contracts" { } ''
-  ${pkgs.nodejs_24}/bin/node ${./.}/build-react-contracts.mjs ${config}
+  ${pkgs.nodejs_24}/bin/node ${buildTools}/build-react-contracts.mjs ${config}
 ''