Load checked installations independently of the running compiler (WI-16)

Keep compiler-dependent checks in Nix builds; load stored plans and programs with original provenance and runtime artifact validation. Allow an identical executable world to receive a new activation epoch after a toolchain rebuild.

Compiler-update/altered-program regression, coordinator and full sandboxed integration checks pass; lint and formatting pass. Default platform/source wiring remains the next task.

src/execution-world/receipts.ts

@@ -119,7 +119,8 @@ export async function checkArtifactReceipt(
       throw new ExecutionPlanError("INVALID_RECEIPT", file.path, "Generated bindings were replaced or omitted");
   }
 }
-/** Activation uses this entrypoint with its trusted generator identity, not the manifest-only loader. */
+/** Checked Nix builds validate generated sources with their selected compiler.
+ * Runtime loading uses the stored outputs instead of repeating compilation. */
 export async function loadCheckedArtifactWorld(
   plan: ExecutionPlan,
   roots: Readonly<Record<string, string>>,