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.

src/capability-language/execution-scaffold.ts

@@ -80,6 +80,7 @@ export async function executionScaffold(
       devShells.default = (import (helpers + "/quixos-package-helpers.nix")).mkCaminoYarnShell { inherit pkgs; };
       quixosPackages.checkedArtifacts = context:
 let
+  pkgs = camino.packageSet { inherit nixpkgs system context; };
   contract = builtins.fromJSON (builtins.readFile context.buildContract);
   package = contract.definition.package;
   portable = builtins.filter (entry: entry.execution.kind != "remote") package.exports;