feat(diary): boot list, help and completion requests quietly (quick-261028-rqc)

- helpOnly also counts no command word, list, help, cobra's shell
  completion requests and --help=<bool>, read the way pflag does
- TestHelpOnlyAgreesWithCobra pins the classification against bonfire's
  real dispatch, with the passthrough --help case as the exception
- console and logging docs describe which invocations boot quietly

modules/diary/export_test.go

@@ -0,0 +1,10 @@
+package diary
+
+// HelpOnly exposes helpOnly to the external tests.
+var HelpOnly = helpOnly
+
+// The completion command names helpOnly recognises, for the cobra check.
+const (
+	CompleteRequestCmd       = completeRequestCmd
+	CompleteNoDescRequestCmd = completeNoDescRequestCmd
+)