accesslog-shipper: emit __shipstat__ sent-line checkpoints for splits reconciliation

The splits completeness floor is TIME-based (trust hours complete since shipper
connect) and blind to event-loss-by-rotation (2026-07-10: raw_events rotated
every 1-2min, cruncher lost ~85% of us-32 events, floor still called the hours
complete). Shipper now injects {"__shipstat__":1,"sess":..,"sent":N,"ts":..}
every 1000 lines or 30s through the SAME tcp pipe. Cruncher diffs shipper-sent
vs DB-ingested per gateway/hour -> a reconciliation-based floor that catches the
loss a clock cannot. sess=connection-start epoch so resets on reconnect are
detectable. Logic in a mounted .awk file (not inline) to dodge sh/awk quoting.
Verified on busybox:1.36 (systime/fflush OK). NOT deployed until claude@'s
cruncher filters __shipstat__ from event parsing - coordinating via SIP.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

accesslog-shipper.awk

@@ -0,0 +1,18 @@
+# Streams dshackle access-log lines unchanged, and every 1000 lines OR 30s
+# injects a __shipstat__ checkpoint carrying the cumulative sent-count for this
+# connection. The splits cruncher (claude host) filters these OUT of event
+# processing and uses them to reconcile shipped-vs-ingested per gateway per hour
+# — the completeness signal the time-based floor cannot see (event-loss-by-
+# rotation, 2026-07-10). `sess` = connection-start epoch so the cruncher detects
+# counter resets on shipper reconnect (retry loop resumes at file END).
+BEGIN { sess = systime(); last = sess; n = 0 }
+{
+    n++
+    print
+    now = systime()
+    if (n % 1000 == 0 || now - last >= 30) {
+        printf "{\"__shipstat__\":1,\"sess\":%d,\"sent\":%d,\"ts\":%d}\n", sess, n, now
+        fflush()
+        last = now
+    }
+}