persist: read-side query helpers — seq/time/type/predicate scans + 9 tests

query.sx: read-between (seq range), read-since/read-window (by :at),
read-by-type, read-where, count-where. Pure scans over persist/read for audit
windows, type filters, since-cursors. 152/152.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/persist/scoreboard.json

@@ -13,9 +13,10 @@
     "view": {"pass": 11, "fail": 0},
     "cas": {"pass": 11, "fail": 0},
     "catalog": {"pass": 10, "fail": 0},
+    "query": {"pass": 9, "fail": 0},
     "recovery": {"pass": 6, "fail": 0}
   },
-  "total_pass": 143,
+  "total_pass": 152,
   "total_fail": 0,
-  "total": 143
+  "total": 152
 }