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>

plans/persist-on-sx.md

@@ -42,7 +42,7 @@ read models (feeds, indices, audit logs) update incrementally.
 
 ## Status (rolling)
 
-`bash lib/persist/conformance.sh` → **143/143** (Phases 1–4 complete + extensions)
+`bash lib/persist/conformance.sh` → **152/152** (Phases 1–4 complete + extensions)
 
 ## Ground rules
 
@@ -158,11 +158,19 @@ over an in-process disk (the mock-IO harness).
   `stream-exists?`/`total-events`. Backend `:streams` op (from seq high-water
   marks, so compacted streams still list), threaded through mem + durable.
 
+- [x] `query.sx` — read-side scans: `read-between` (seq range), `read-since`/
+  `read-window` (by `:at`), `read-by-type`, `read-where`, `count-where`. Pure
+  reads for audit windows / type filters / since-cursors.
+
 ## Consumers (post-foundation, not in scope here)
 feed/-log, flow store, mod/audit, search index, acl grants, identity sessions all
 become `persist` log or kv. Track each migration in that subsystem's plan.
 
 ## Progress log
+- **Ext: read-side query helpers (152/152).** `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 ad-hoc relational queries
+  consumers still project into a kv read model. 9 tests incl. durable.
 - **Ext: stream catalog (143/143).** New backend op `:streams` (keys of the seq
   high-water-mark dict, threaded through mem-backend + durable serve/io-backend)
   so fully-compacted streams still enumerate. `catalog.sx`: