sx-git Phase 3: commit DAG — log/ancestry/merge-base SX-side + Datalog bridge (TDD)

Topo log = reverse DFS postorder over parent edges from commit objects;
reflexive is-ancestor?, all-LCA merge-bases (criss-cross verified). Datalog
bridge exports (git-parent child parent) facts under a minimal 2-rule
ancestor closure, cross-checked against the SX walk. 30/30, total 106/106.

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

lib/git/conformance.sh

@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(object ref)
+SUITES=(object ref dag)
 
 OUT_JSON="lib/git/scoreboard.json"
 OUT_MD="lib/git/scoreboard.md"
@@ -32,8 +32,19 @@ run_suite() {
 (load "lib/persist/log.sx")
 (load "lib/persist/kv.sx")
 (load "lib/artdag/dag.sx")
+(load "lib/datalog/tokenizer.sx")
+(load "lib/datalog/parser.sx")
+(load "lib/datalog/unify.sx")
+(load "lib/datalog/db.sx")
+(load "lib/datalog/builtins.sx")
+(load "lib/datalog/aggregates.sx")
+(load "lib/datalog/strata.sx")
+(load "lib/datalog/eval.sx")
+(load "lib/datalog/api.sx")
+(load "lib/datalog/magic.sx")
 (load "lib/git/object.sx")
 (load "lib/git/ref.sx")
+(load "lib/git/dag.sx")
 (epoch 2)
 (eval "(define git-test-pass 0)")
 (eval "(define git-test-fail 0)")