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.

docs/Makefile

@@ -1,38 +1,26 @@
-override SHELL := /bin/sh
-override MAKEFLAGS += --no-print-directory
+SHELL := /bin/sh
+MAKEFLAGS += --no-print-directory
 
 .DEFAULT_GOAL := help
 .DELETE_ON_ERROR:
 
-override MDBOOK := mdbook
-
-override PRIMARY_GOAL := $(firstword $(MAKECMDGOALS))
-
-ifeq ($(PRIMARY_GOAL),run)
-
-.PHONY: run
-
-# Application arguments may also look like Make goals. The run recipe recovers
-# their exact boundaries from the original invocation.
-.DEFAULT:
-	@:
-
-else
-
-.PHONY: help run check
+.PHONY: help build test check clean
 
 help:
-	@printf '%s\n' 'Usage: make docs -- <mdbook arguments...>' '' \
-		'With no arguments, mdbook test and mdbook build are run.' \
-		'Example: make docs -- build' '' \
-		'Project target:' \
-		'  check  Run mdbook test and mdbook build'
+	@printf '%s\n' 'Usage: make -C docs build|test|check|clean' '' \
+		'  build  Build the book' \
+		'  test   Test book examples' \
+		'  check  Test and build the book' \
+		'  clean  Remove generated documentation' '' \
+		'For other options, run mdbook directly from docs/.'
 
-endif
+build:
+	mdbook build
 
-check:
-	$(MDBOOK) test
-	$(MDBOOK) build
+test:
+	mdbook test
 
-run:
-	@exec python3 ../scripts/make-argv.py exec run $(MDBOOK)
+check: test build
+
+clean:
+	mdbook clean