fix(artifact): put binary macro before merge=ours in generated .gitattributes

gitattributes apply left to right and the binary macro expands to
-diff -merge -text, so the generated line

    graph.db.zst merge=ours binary

leaves the merge attribute UNSET (git check-attr merge reports
"unset"), and concurrent artifact refreshes produce a binary merge
conflict instead of auto-resolving -- the exact failure this file is
generated to prevent. Reordering to

    graph.db.zst binary merge=ours

makes check-attr report merge: ours while keeping -diff/-text intact.

Verified on a real repository: before the reorder git check-attr merge
-- .codebase-memory/graph.db.zst printed "unset"; after, "ours".

Extends artifact_gitattributes_created to pin the ordering so the
regression cannot return.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: Alex <plosceac.alexandre@gmail.com>

Author: alex-plosceac

src/pipeline/artifact.c

@@ -382,9 +382,13 @@ static void ensure_gitattributes(const char *repo_path) {
     } else {
         FILE *fp = fdopen(fd, "w");
         if (fp) {
+            /* Order matters: attributes apply left to right and the `binary`
+             * macro expands to `-diff -merge -text`, so a trailing `binary`
+             * unsets `merge=ours` and the conflict prevention this file
+             * exists for never engages. The macro must come first. */
             (void)fputs("# Auto-generated by codebase-memory-mcp\n"
                         "# Prevent merge conflicts on compressed artifact\n" CBM_ARTIFACT_FILENAME
-                        " merge=ours binary\n",
+                        " binary merge=ours\n",
                         fp);
             (void)fclose(fp);
         } else {

tests/test_artifact.c

@@ -242,6 +242,20 @@ TEST(artifact_gitattributes_created) {
     struct stat st;
     ASSERT_EQ(stat(ga, &st), 0);
 
+    /* Attribute ORDER is load-bearing: gitattributes apply left to right and
+     * the `binary` macro expands to `-diff -merge -text`, so a trailing
+     * `binary` unsets a preceding `merge=ours` (git check-attr merge reports
+     * "unset" and concurrent artifact refreshes produce binary conflicts
+     * instead of auto-resolving). The driver must come after the macro. */
+    FILE *gaf = fopen(ga, "r");
+    ASSERT_NOT_NULL(gaf);
+    char content[512] = {0};
+    size_t rd = fread(content, 1, sizeof(content) - 1, gaf);
+    (void)fclose(gaf);
+    ASSERT_TRUE(rd > 0);
+    ASSERT_NOT_NULL(strstr(content, CBM_ARTIFACT_FILENAME " binary merge=ours"));
+    ASSERT_TRUE(strstr(content, "merge=ours binary") == NULL);
+
     cleanup_dir(g_tmpdir);
     PASS();
 }