build: replace argument dispatch and retain source-bound verification

Replace argument recovery with direct build targets. Run host, target,
board, coverage, Miri and selected Kani checks while retaining source
identities, logs and artifacts, including failed attempts.

Keep the PID proof diagnostic exception explicit and match its exact
identity alongside passing contract assertions and covers.

Validation: final-source verification matrix, assembled workflow tests
and documentation build.

flake.nix

@@ -23,8 +23,10 @@
             packages = [
               pkgs.rustup
               pkgs.gcc
+              pkgs.cargo-llvm-cov
               pkgs.dfu-util
               pkgs.mdbook
+              pkgs.nodejs
               pkgs.ripgrep
               pkgs.ruff
               pkgs.shfmt