P5B Execution Plan

Add config normalization for nativeRoadPackage, migrate two supported configs and the template.
Add the tested ZIP importer with bounded extraction, root-flat/path/symlink validation, SHA cache and manifest/area validation.
Route Blender, preview traffic, stage manifests and diagnostics through the imported descriptor.
Delete compiler CLI/compile production paths and package dependency; replace their tests with ZIP fixture and negative importer tests.
Update docs/specs, run native/legacy unit suites, build two exported packages, then run Blender parity.

Rollback: restore the old compiler dependency and native compile path in one revert; ZIP exports remain non-destructive standalone files.