persist: projections — fold stream into read model, incremental resume + 9 tests

project.sx: projection state {:value :seq}; persist/project folds the whole
stream, persist/project-resume folds only the tail so read models update
incrementally. Pure step (value event)->value. 37/37.

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

lib/persist/conformance.sh

@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(event log kv)
+SUITES=(event log kv project)
 
 OUT_JSON="lib/persist/scoreboard.json"
 OUT_MD="lib/persist/scoreboard.md"
@@ -31,6 +31,7 @@ run_suite() {
 (load "lib/persist/backend.sx")
 (load "lib/persist/log.sx")
 (load "lib/persist/kv.sx")
+(load "lib/persist/project.sx")
 (load "lib/persist/api.sx")
 (epoch 2)
 (eval "(define persist-test-pass 0)")