fix(python): give NewContext identities the browser's Firefox version

NewContext() and AsyncNewContext() passed ff_version=None through to
generate_context_fingerprint(), so a context's user agent kept the version
fpgen drew (e.g. Firefox/146) while the browser underneath was 152. They
now default ff_version to the major version of Playwright's
Browser.version, which Juggler reports from MOZ_APP_VERSION_DISPLAY, so the
UA always names the browser the page is actually talking to. An explicit
ff_version still wins.

The docstrings said each context gets "its own real fingerprint preset";
the default has been an fpgen draw, with a preset only when one is passed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pythonlib/tests/test_new_context_version.py

@@ -0,0 +1,36 @@
+"""A context's user agent carries the Firefox version of the browser it runs in.
+
+Without an explicit ff_version, NewContext kept whatever version fpgen drew
+(e.g. Firefox/146) on a 160 browser, so the UA disagreed with every
+version-dependent API the page could probe.
+"""
+
+import asyncio
+import re
+from unittest import mock
+
+import pytest
+
+from camoufox import async_api, sync_api
+
+
+def _user_agent(init_script):
+    return re.search(r'setNavigatorUserAgent\("([^"]+)"\)', init_script).group(1)
+
+
+@pytest.mark.parametrize("api", ["sync", "async"])
+def test_user_agent_matches_the_browser_version(api):
+    context = mock.MagicMock()
+    browser = mock.MagicMock()
+    # Playwright's Browser.version for Firefox: MOZ_APP_VERSION_DISPLAY.
+    browser.version = "160.0.1"
+    if api == "sync":
+        browser.new_context.return_value = context
+        sync_api.NewContext(browser, os="linux")
+    else:
+        context.add_init_script = mock.AsyncMock()
+        browser.new_context = mock.AsyncMock(return_value=context)
+        asyncio.run(async_api.AsyncNewContext(browser, os="linux"))
+
+    user_agent = _user_agent(context.add_init_script.call_args.args[0])
+    assert "Firefox/160.0" in user_agent and "rv:160.0" in user_agent, user_agent

pythonlib/tests/test_proxy_geo.py

@@ -34,6 +34,7 @@ EXIT = {"status": "success", "query": "203.0.113.7", "timezone": "Europe/Paris"}
 
 def _sync_browser():
     browser = mock.MagicMock()
+    browser.version = "152.0.4"
     return browser
 
 
@@ -41,6 +42,7 @@ def _async_browser():
     context = mock.MagicMock()
     context.add_init_script = mock.AsyncMock()
     browser = mock.MagicMock()
+    browser.version = "152.0.4"
     browser.new_context = mock.AsyncMock(return_value=context)
     return browser