kdesc --coverage <target>: one target's view (from dev 931ea5490a5d)

For the designer building a target: the klammers that cover it, those
that do so with an empty definition (a decision that the klammer has no
meaning there), and the undecided ones (no definition). One klammer per
line, alphabetical; "all" adds the explanations; an unknown word names
the missing target.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

mac/coverage.h

@@ -89,6 +89,7 @@ struct Klammer_coverage
     // definitions are spread over several files lists them all.  Shown by
     // "--coverage -v", and only on a row that names ONE klammer.
     std::vector<std::string> m_files {};
+    std::vector<std::string> m_empty {};   // targets whose written definition has an empty body
 };
 
 // Compute the coverage of every klammer the machine has loaded.  Analysis
@@ -116,3 +117,8 @@ std::vector<Klammer_coverage> klammer_coverage(const Machine& machine,
 void report_coverage(const Machine& machine,
                      const std::vector<Klammer_coverage>& coverage,
                      bool full, std::ostream& os);
+// One target's view: which klammers cover it, which do so with an empty
+// definition (a decision that the klammer has no meaning there), and which
+// are undecided (no definition -- nothing decided either way).
+void report_target_coverage(const std::vector<Klammer_coverage>& coverage,
+                            const std::string& target, bool full, std::ostream& os);