sx-git extension: git-wire import — the inverse adapter, round-trip law (TDD)

lib/git/import.sx parses loose payloads back to native objects bottom-up
over an export-set table: tree mode/name/raw-sha triples, ident lines,
header/message split, committer stored only when distinct so export
defaults regenerate identical bytes. Laws verified: export->import->export
is BYTE-IDENTICAL (head sha + every object), imported blobs/default-mode
trees regain their original native cids, 100755/tags/distinct-committer/
multi-line messages all survive. 15/15, total 267/267.

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 dag worktree diff merge porcelain export)
+SUITES=(object ref dag worktree diff merge porcelain export import)
 
 OUT_JSON="lib/git/scoreboard.json"
 OUT_MD="lib/git/scoreboard.md"
@@ -51,6 +51,7 @@ run_suite() {
 (load "lib/git/porcelain.sx")
 (load "lib/git/sha1.sx")
 (load "lib/git/export.sx")
+(load "lib/git/import.sx")
 (epoch 2)
 (eval "(define git-test-pass 0)")
 (eval "(define git-test-fail 0)")