fix(fk): compound-FK violation message names every column pair

ADR-0043 residual: a compound-FK violation's friendly error named only the
first child->parent column pair (the ADR-0019 facts model is single-column).
enrich_fk_violation now gathers all pairs of the matched relationship and
carries them comma-joined in the existing single-column facts slots, so the
headline reads e.g. "no parent row in `Region` has `country, code` = `7, 8`."
instead of naming just `country`.

Single-column behaviour is unchanged (a one-element join is the element
itself). No facts-model or catalog change -- the joined strings flow through
the existing `{parent_column}` / `{value}` placeholders.

Tests: enrichment facts (compound names every pair, single-column
regression) + translate rendering (headline names both columns). 2211 pass
/ 0 fail / 1 ignored. Clippy clean.

src/friendly/translate.rs

@@ -882,6 +882,30 @@ mod tests {
         assert!(f.headline.contains("`99`"));
     }
 
+    #[test]
+    fn fk_child_side_renders_every_column_of_a_compound_key() {
+        // ADR-0043 residual: a compound-FK violation carries the
+        // comma-joined column + value lists in the single-column facts
+        // slots, so the headline names every pair, not just the first.
+        let err = sqlite(
+            "FOREIGN KEY constraint failed",
+            SqliteErrorKind::UniqueViolation,
+        );
+        let mut ctx = ctx_with(Operation::Insert);
+        ctx.parent_table = Some("Region".to_string());
+        ctx.parent_column = Some("country, code".to_string());
+        ctx.value = Some("7, 8".to_string());
+        let f = translate(&err, &ctx);
+        assert!(f.headline.contains("no parent row"), "child-side: {}", f.headline);
+        assert!(f.headline.contains("Region"));
+        assert!(
+            f.headline.contains("country, code"),
+            "both parent columns must appear: {}",
+            f.headline
+        );
+        assert!(f.headline.contains("`7, 8`"), "joined value: {}", f.headline);
+    }
+
     #[test]
     fn fk_with_delete_op_renders_parent_side_wording() {
         let err = sqlite(