fix(quote): count unversioned quote requests on arrival, and say so

The unversioned-quote counter is what ADR-0013 names as the input to the
decision to retire the legacy quote path. It increments when the request
arrives, before validation and before a quote is generated, so a request
the node then refuses is counted too. The log line claimed the opposite,
reporting a running total of quotes "served": a node turning away a
thousand oversized unversioned requests would report having served a
thousand quotes, and that number is meant to decide when the legacy path
can be closed.

Arrival is the right place to count. The question the number answers is
how many clients still cannot declare a settlement version, and a client
whose request failed for an unrelated reason is still one of them and
would still break if the path were retired. So this renames the counter
and rewords the log line to match where it fires, rather than moving the
increment, and records the same in the ADR.

No behavioural change.

Author: grumbach

docs/adr/ADR-0013-settlement-version-and-pre-payment-compatibility.md

@@ -96,7 +96,7 @@ A refusal is a verdict about the client, not about one peer, so it cannot be tre
 
 ### Unversioned requests are still served
 
-A storer cannot distinguish a client that settles correctly but predates the version field (ant-core 0.5.1 through 0.6.0) from one that does not. Refusing both would break clients that are behaving, so unversioned requests are served and counted. Nodes log a running total per path under `ant_node::quote::settlement`.
+A storer cannot distinguish a client that settles correctly but predates the version field (ant-core 0.5.1 through 0.6.0) from one that does not. Refusing both would break clients that are behaving, so unversioned requests are served and counted. Nodes log a running total per path under `ant_node::quote::settlement`. The count is taken on arrival rather than on a quote being returned: a request this node refuses for an unrelated reason still came from a client that cannot declare a version, and would still break if the unversioned path were retired.
 
 Flipping that to a refusal is a **follow-up**, gated on that count decaying, and should use a dated self-retiring boundary in the style of `MERKLE_PARITY_ENFORCED_FROM_UNIX`.
 

src/storage/handler.rs

@@ -211,19 +211,24 @@ impl Drop for GetRequestTelemetry {
     }
 }
 
-/// How many unversioned quote requests to serve between adoption log lines.
+/// How many unversioned quote requests to receive between adoption log lines.
 ///
 /// One line per request would drown the log at production quote rates, and one
 /// line total would say nothing about the trend. A running count emitted every
 /// `N` gives the shape of client adoption, which is the number that decides
 /// when unversioned requests can start being refused outright.
 const UNVERSIONED_QUOTE_LOG_INTERVAL: u64 = 1_000;
 
-/// Unversioned quote requests served since start, by path.
+/// Unversioned quote requests received since start, by path.
+///
+/// Counted on arrival, before the quote is generated, because the question
+/// this answers is how many clients still cannot declare a version. A request
+/// this node then refuses for an unrelated reason still came from such a
+/// client, and would still break if the unversioned path were retired.
 ///
 /// Indices are `[single_node, merkle]`. A plain counter rather than a metric
 /// because the only consumer is the rollout decision, and that reads logs.
-static UNVERSIONED_QUOTES_SERVED: [AtomicU64; 2] = [AtomicU64::new(0), AtomicU64::new(0)];
+static UNVERSIONED_QUOTE_REQUESTS: [AtomicU64; 2] = [AtomicU64::new(0), AtomicU64::new(0)];
 
 /// Refuse a quote when the requesting client settles under rules this node no
 /// longer accepts. `None` means the request may proceed.
@@ -903,15 +908,16 @@ impl AntProtocol {
     /// the clients that were already going to lose their money.
     fn note_unversioned_quote(path: &str) {
         let slot = usize::from(path == "merkle");
-        let Some(counter) = UNVERSIONED_QUOTES_SERVED.get(slot) else {
+        let Some(counter) = UNVERSIONED_QUOTE_REQUESTS.get(slot) else {
             return;
         };
-        let served = counter.fetch_add(1, Ordering::Relaxed).saturating_add(1);
-        if served % UNVERSIONED_QUOTE_LOG_INTERVAL == 0 {
+        let seen = counter.fetch_add(1, Ordering::Relaxed).saturating_add(1);
+        if seen % UNVERSIONED_QUOTE_LOG_INTERVAL == 0 {
             info!(
                 target: "ant_node::quote::settlement",
-                "Served {served} {path} quotes to clients that declare no settlement version. \
-                 These clients cannot be told to upgrade before they pay.",
+                "Received {seen} {path} quote requests from clients that declare no \
+                 settlement version. These clients cannot be told to upgrade before \
+                 they pay.",
             );
         }
     }