astgen: blockExpr rvalue, local_ptr rvalue, array_mult

- blockExpr: call rvalue on void result for unlabeled blocks, matching
  upstream AstGen.zig:2431. This was causing a missing STORE_NODE when
  empty blocks like {} were used as struct field values with pointer RL.
- identifierExpr: call rvalueNoCoercePreRef after LOAD in local_ptr case,
  matching upstream AstGen.zig:8453-8454.
- Implement AST_NODE_ARRAY_MULT (** operator) with ArrayMul payload,
  matching upstream AstGen.zig:774-785.
- Enable parser_test.zig and astgen_test.zig corpus tests.
- Enable combined corpus test (all 5 files pass).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

stage0/astgen_test.zig

@@ -256,6 +256,32 @@ fn expectEqualZir(gpa: Allocator, ref: Zir, got: c.Zir) !void {
                     @as(i32, @intCast(got_counts[t])) - @as(i32, @intCast(ref_counts[t])),
                 });
         }
+        // Find first tag divergence.
+        const min_len = @min(ref_len, got.inst_len);
+        for (0..min_len) |i| {
+            const ref_tag: u8 = @intFromEnum(ref_tags[i]);
+            const got_tag: u8 = @intCast(got.inst_tags[i]);
+            if (ref_tag != got_tag) {
+                std.debug.print("first divergence at [{d}]: ref_tag={d} got_tag={d}\n", .{ i, ref_tag, got_tag });
+                // Show ref instruction data for this position.
+                const rd = ref_datas[i];
+                std.debug.print("  ref pl_node: src_node={d} payload={d}\n", .{
+                    rd.pl_node.src_node, rd.pl_node.payload_index,
+                });
+                // Scan for nearest declaration.
+                var j: usize = i;
+                while (j > 0) {
+                    j -= 1;
+                    if (ref_tags[j] == .declaration) {
+                        std.debug.print("  nearest decl at [{d}]: src_node={d}\n", .{
+                            j, ref_datas[j].declaration.src_node,
+                        });
+                        break;
+                    }
+                }
+                break;
+            }
+        }
         return error.TestExpectedEqual;
     }
 
@@ -817,9 +843,6 @@ test "astgen: corpus tokenizer_test.zig" {
 }
 
 test "astgen: corpus parser_test.zig" {
-    // TODO: 10+ extra data mismatches (ref=48 got=32, bit 4 = propagate_error_trace)
-    // in call instruction flags — ctx propagation differs from upstream.
-    if (true) return error.SkipZigTest;
     const gpa = std.testing.allocator;
     try corpusCheck(gpa, @embedFile("parser_test.zig"));
 }
@@ -857,7 +880,7 @@ test "astgen: struct init typed" {
 }
 
 test "astgen: corpus" {
-    if (true) return error.SkipZigTest; // TODO: parser_test.zig fails
+    // All individual corpus tests now pass.
     const gpa = std.testing.allocator;
 
     var any_fail = false;