fix(fk): inline FK referencing a compound PK points at the table-level form

ADR-0043 D4 residual: an inline column-level FK (`<col> REFERENCES P(a,b)`)
is single-column by construction, so referencing a parent's compound PK
gave the generic arity error ("1 foreign-key column(s) on the child side,
but `P`'s key has 2..."). It now points the user at the table-level form:
"an inline column reference can only name one column ... Use the table-level
form instead: FOREIGN KEY (<columns>) REFERENCES P (a, b)".

- Adds `inline: bool` to SqlForeignKey, set by the grammar's single shared
  builder consume_fk_reference (true for the inline path, false for the
  table-level and ALTER paths).
- resolve_fk_parent_columns takes `inline` and tailors the arity-mismatch
  message when an inline FK meets a compound key.

Tests: parse-layer (inline=true / table-level=false) + end-to-end worker
refusal wording. 2209 pass / 0 fail / 1 ignored. Clippy clean.

src/dsl/grammar/ddl.rs

@@ -1557,7 +1557,7 @@ fn build_sql_create_table(path: &MatchedPath, source: &str) -> Result<Command, V
                 // Inline FK is single-column (the column it sits on);
                 // a compound FK uses the table-level form (ADR-0043 D4).
                 let child_column = columns.last().map_or_else(String::new, |c| c.name.clone());
-                foreign_keys.push(consume_fk_reference(&mut items, None, vec![child_column]));
+                foreign_keys.push(consume_fk_reference(&mut items, None, vec![child_column], true));
             }
             // Table-level `[constraint <name>] foreign key (<col>)
             // references <parent> [(<col>)] [on …]` (ADR-0035 §5, 4b).
@@ -1587,7 +1587,8 @@ fn build_sql_create_table(path: &MatchedPath, source: &str) -> Result<Command, V
                 if matches!(items.peek().map(|i| &i.kind), Some(MatchedKind::Word("references"))) {
                     items.next();
                 }
-                let fk = consume_fk_reference(&mut items, pending_fk_name.take(), child_columns);
+                let fk =
+                    consume_fk_reference(&mut items, pending_fk_name.take(), child_columns, false);
                 foreign_keys.push(fk);
             }
             // Track paren depth for element-boundary detection. The
@@ -1704,6 +1705,7 @@ fn consume_fk_reference<'a, I>(
     items: &mut std::iter::Peekable<I>,
     name: Option<String>,
     child_columns: Vec<String>,
+    inline: bool,
 ) -> SqlForeignKey
 where
     I: Iterator<Item = &'a crate::dsl::walker::outcome::MatchedItem>,
@@ -1752,6 +1754,7 @@ where
         parent_columns,
         on_delete,
         on_update,
+        inline,
     }
 }
 
@@ -2454,7 +2457,8 @@ fn build_alter_fk(path: &MatchedPath) -> SqlForeignKey {
     if matches!(items.peek().map(|i| &i.kind), Some(MatchedKind::Word("references"))) {
         items.next();
     }
-    consume_fk_reference(&mut items, None, child_columns)
+    // `ALTER TABLE … ADD FOREIGN KEY (…)` is the table-level form.
+    consume_fk_reference(&mut items, None, child_columns, false)
 }
 
 pub static SQL_ALTER_TABLE: CommandNode = CommandNode {