tools (volt): claim coverage 2 of 9 -> 8 of 9, and the sweep stops tripping the census

Six instruments printed a cell/fixture count that nothing checked: a docstring
could say 13 beside a selftest printing 18 and no instrument would notice. Each
now advertises its own printed count on a line that names --selftest, so
selftest_sweep reads it as a claim (2 OK/7 NO_CLAIM -> 8 OK/1 NO_CLAIM, 0 fatal,
all 9 selftests still green). doc_census_check.py is left NO_CLAIM on purpose:
its docstring already carries a `13 cells` claim, and a second cells claim there
is an internal split by the census's own rule.

selftest_sweep.py's own docstring quoted a fixture line ("selftest: 7 cells ...")
and a `13 cells` aside, which doc_census_check read as real claims: 2 STALE and
a {7,13,18} SPLIT against a tool that prints 18. Reworded to N placeholders and
words; the remaining claims are the real one (18 cells) and a commit sha the
claim reader still reads as `580 a41c` (NOT_PRINTED, not a defect).

tools/citation_resolve_check.py

@@ -111,7 +111,7 @@ WORKED CATCH -- this tool's first finding is one of MY OWN artifacts
 USAGE
   python3 citation_resolve_check.py [--repo DIR] [--rev HEAD] [--corpus PATH...]
       [--json OUT] [--only stale|asself|unresolved|ambiguous|external|externalnamed|named|all]
-      [--context] [--selftest]
+      [--context] [--selftest]        # 11 fixtures
 """
 import argparse
 import collections