fix: recognize LICENSE / COPYING / etc. as text files

istextorbinary returns null for filenames with no extension, and the
isTextFile() guard treated null as "not text" — so terms in LICENSE,
COPYING, AUTHORS, README (extensionless), CHANGELOG, NOTICE, and
similar conventional filenames went through the binary passthrough
in AnonymizeTransformer and were never anonymized.

Add a small whitelist of these names ahead of the istextorbinary call.

Fixes #493.

test/is-text-file.test.js

@@ -0,0 +1,30 @@
+const { expect } = require("chai");
+require("ts-node/register/transpile-only");
+const { isTextFile } = require("../src/core/anonymize-utils");
+
+describe("isTextFile", function () {
+  // #493 — istextorbinary returns null for files with no extension, so a
+  // bare LICENSE / COPYING / etc. used to be classified as binary and
+  // never anonymized. Whitelist the conventional plaintext filenames.
+  it("recognizes conventional no-extension plaintext filenames", function () {
+    expect(isTextFile("LICENSE")).to.equal(true);
+    expect(isTextFile("license")).to.equal(true);
+    expect(isTextFile("COPYING")).to.equal(true);
+    expect(isTextFile("AUTHORS")).to.equal(true);
+    expect(isTextFile("README")).to.equal(true);
+    expect(isTextFile("CHANGELOG")).to.equal(true);
+    expect(isTextFile("NOTICE")).to.equal(true);
+    expect(isTextFile("path/to/LICENSE")).to.equal(true);
+  });
+
+  it("still recognizes well-known text extensions", function () {
+    expect(isTextFile("foo.txt")).to.equal(true);
+    expect(isTextFile("foo.md")).to.equal(true);
+    expect(isTextFile("foo.js")).to.equal(true);
+  });
+
+  it("does not classify binary files as text", function () {
+    expect(isTextFile("foo.png")).to.equal(false);
+    expect(isTextFile("foo.zip")).to.equal(false);
+  });
+});