fix: make maintainer tool output actionable

--emulator accepts a buildbot core name from a profile's cores:, and a
mistyped target gets the closest names instead of every target. diff_truth
shows destinations and reports unpaired entries as evidence, not removals.
The verify summary counts discrepancies, a shared destination names both
systems, a truth hash conflict names both cores, and pipeline steps carry
their place in the real run instead of N/8. Every GitHub API caller takes
the token from github_token(), which falls back to gh auth token.

scripts/check_freshness.py

@@ -1241,7 +1241,12 @@ def render(findings: list[Finding]) -> str:
 
 def main() -> int:
     parser = argparse.ArgumentParser(allow_abbrev=False, description=__doc__.split("\n\n")[0])
-    parser.add_argument("--only", help="comma-separated areas: " + ",".join(AREAS))
+    # Joined with ", " so argparse wraps between names: one comma-joined
+    # token was cut inside "coreinfo".
+    parser.add_argument(
+        "--only", metavar="AREAS",
+        help="comma-separated areas, among: " + ", ".join(AREAS),
+    )
     parser.add_argument("--json", action="store_true", help="machine-readable output")
     parser.add_argument(
         "--profiles", action="store_true",