V40 Gate 3: Add unit coverage inventory

Adds the package-backed V40 unit coverage inventory, deterministic artifact, generator and gate check scripts, protocol exports, focused tests, workflow wiring, and spec/roadmap documentation for package, primitive, interface-helper, Reading implementation, and demonstration-boundary unit coverage closure.

Author: geraldarthurdavis

.bitcode/v40-test-inventory-coverage-matrix.json

@@ -423,7 +423,7 @@
       "passed": true
     },
     {
-      "id": "roadmap-advanced-to-gate2",
+      "id": "roadmap-advanced-through-gate2",
       "sourcePath": "SPECIFICATIONS_ROADMAP.md",
       "passed": true
     },