[Amadeus-22]

Closes #679.

• --extra-docker-config '{"environment": ["JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF-8", "TOKEN=abc=="]}' passed {"JAVA_TOOL_OPTIONS": "-Dfile.encoding", "TOKEN": "abc"} to the container: LeanRunner.parse_extra_docker_config split KEY=VALUE strings on every = and kept the first two parts.
• They are now split on the first = only, as Docker does. Entries given as [key, value] pairs and the dict form are unchanged.
• Added a test with a JVM -D option and a base64-padded value. It fails on master and passes with the fix.
• pytest tests/components/docker tests/commands/test_backtest.py tests/commands/test_research.py passes (119 passed, 6 skipped, Python 3.12) and python static_analysis.py is clean.

🤖 Generated with Claude Code

[quantconnect-kronos-reviewer]

Approving. The fix is correct, small and covered by a test.

• item.split("=", 1) matches how Docker handles -e KEY=VALUE: it splits on the first = only. I checked that docker run -e TOKEN=abc== -e J=-Da=b gives TOKEN=abc== and J=-Da=b inside the container. The Docker SDK turns the resulting dict back into KEY=VALUE with the value unchanged (docker.utils.format_environment), so the value reaches the container intact.
• The change only affects KEY=VALUE strings in the list form. [key, value] pairs, the dict form and KEY= (empty value) behave as before. A bare KEY with no = still raises IndexError, just as it did on master. Docker would pass the host's value through in that case, but that is outside this issue and can go in its own PR if anyone wants it.
• The single helper is shared by backtest, live, optimize, research and private-cloud start, so all of them get the fix.
• The new test checks the exact output for a JVM -D option and a base64-padded value. CI passes on every OS and Python version.

No other repositories need updating.