…download for tests

- Fix CefSSLInfo.statusBiset typo to statusBitset
- Refactor SelfSignedSSLTest to use named inner classes instead of anonymous
  classes, fixing field access issues with the TestFrame template method pattern
- Add TestFrame(String startURL) constructor for direct browser URL setup
- Add automatic native binary download from tlappe/jcefbuild GitHub releases
  via NativesInstaller, integrated into TestSetupExtension using
  SystemBootstrap.setLoader() for absolute path loading
- Add jcef-natives/ to .gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

onTitleChange and onAddressChange can be called multiple times
(e.g. during browser close). Use an early return guard instead of
assertFalse to prevent assertion failures on subsequent calls.
Also fix assertEquals argument order in onAddressChange.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

getFileNames returns display names ("File 1"), not paths.
The test was verifying paths, so it should use getFilePaths
which was added in a prior commit (CefDragData.getFilePaths).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Chromium 143 treats localhost/loopback and private IPs as
"potentially trustworthy origins" and silently accepts self-signed
certificates without calling onCertificateError. Additionally,
valid self-signed certs (not expired) are accepted on mapped domains.

Changes:
- Use --host-resolver-rules to map a fictitious domain
  (jcef-test.invalid) to 127.0.0.1, forcing Chromium to treat
  the connection as external
- Generate an expired self-signed certificate programmatically
  to ensure Chromium triggers onCertificateError
- Add terminateTest() call in onLoadError for certificateRejected
- Make sslInfo and boolean flags volatile for cross-thread visibility
- Bind HTTPS server explicitly to 127.0.0.1 with TLSv1.2

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Remove ProcessEnvironment reflection hack (not needed with JDK in PATH)
- Keep SystemBootstrap.setLoader for CEF natives (absolute path loading)
- Add --host-resolver-rules flag to map jcef-test.invalid to 127.0.0.1
  for SSL certificate error testing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

The root cause of onCertificateError not firing was the old
JetBrains-generated JKS certificate (valid until 2042) being
silently accepted by Chromium 143. The programmatically generated
expired certificate is sufficient to trigger the callback, even
on localhost. No host-resolver-rules hack needed.

Also removes the unused JKS_BASE64 constant and makeKeyStore method.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>