fix(python): classify historical headers and signed flags

Fixes #6568, #6487

src/domain/python/pythonPyc.test.ts

@@ -9,18 +9,30 @@ it("maps pinned CPython 3.7–3.13 magics and leaves gaps unknown", () => {
   expect(pythonPycMagicEntry(3394)).toEqual({
     python_version: "3.7",
     code_layout: "py37",
+    header_bytes: 16,
+  });
+  expect(pythonPycMagicEntry(3390)).toMatchObject({
+    python_version: "3.7",
+    header_bytes: 12,
+  });
+  expect(pythonPycMagicEntry(3391)).toMatchObject({
+    python_version: "3.7",
+    header_bytes: 12,
   });
   expect(pythonPycMagicEntry(3413)).toEqual({
     python_version: "3.8",
     code_layout: "py38",
+    header_bytes: 16,
   });
   expect(pythonPycMagicEntry(3531)).toEqual({
     python_version: "3.12",
     code_layout: "py311",
+    header_bytes: 16,
   });
   expect(pythonPycMagicEntry(3571)).toEqual({
     python_version: "3.13",
     code_layout: "py311",
+    header_bytes: 16,
   });
   expect(pythonPycMagicEntry(3450)).toBeNull();
   expect(pythonPycMagicEntry(62171)).toBeNull();