otel: say which of processes/process is configured

They differ by one letter and a grep for the shorter name matches both.
The summary is what ships; the per-process scraper is deliberately absent,
and a reader (human or grep) cannot tell from the diff alone.

nix/host-modules/otel.nix

@@ -390,6 +390,12 @@ in
                 disk = { };
                 network = { };
                 paging = { };
+                # ⚠️ `processes` is the SUMMARY -- how many are running,
+                # blocked, sleeping. A handful of series per host. Its
+                # singular sibling `process` is the per-process one and is
+                # deliberately absent above; the two differ by one letter and
+                # a grep for the shorter name matches both, so read the
+                # trailing `s` before concluding which is configured here.
                 processes = { };
                 system = { };
               };