fix: reject JDK < 11 early with clear error message

[mashraf-222]

Problem

When running codeflash with JDK 8, the pipeline fails late with a cryptic UnsupportedClassVersionError from the runtime JAR (class version 55.0 requires JDK 11+). The error gives no guidance about what version is needed.

Root Cause

ensure_runtime_environment() in support.py detects the Java version via _detect_java_version() but never validates it meets the minimum requirement (JDK 11). The version is stored for API payloads but not checked.

Fix

Added a version check immediately after _detect_java_version(): if major version < 11, logs a clear error message explaining that JDK 11+ is required and returns False. This stops the pipeline before it hits the cryptic class version error.

Test Coverage

3 new tests in TestJdkVersionCheck:

• test_jdk8_rejected: JDK 8 returns False
• test_jdk11_accepted: JDK 11 returns True
• test_jdk21_accepted: JDK 21 returns True

Testing

$ uv run pytest tests/test_languages/test_java/test_support.py::TestJdkVersionCheck -v
3 passed