Run the CI cyclomatic complexity check to verify __curversion_next_single_key is now below 98 CCN. Update any relevant comments in the file to reflect the new helper structure. Ensure the refactor did not introduce any regressions by running the full test suite.

Tasks

• src/cursor/cur_version.c — Update the function-level comment for __curversion_next_single_key to briefly mention the helper organization (criterion: comment describes the three-phase structure with helper references)
• test/evergreen/cyclomatic-complexity.sh — Run the script from the build directory to measure final CCN (criterion: script completes without failing on __curversion_next_single_key)
• All tests — Run full cursor test suite via python3 ../test/suite/run.py -j8 (criterion: no new failures introduced)
• Validation — Run cd dist && ./s_all to ensure code formatting and validation passes (criterion: no new errors)

Files to create or modify

• src/cursor/cur_version.c — Update function comment for __curversion_next_single_key

Definition of Done

• __curversion_next_single_key CCN is below 98 as measured by test/evergreen/cyclomatic-complexity.sh with Metrix++
• lizard -l c src/cursor/cur_version.c | grep __curversion_next_single_key shows CCN <= 95
• Updated documentation comment present in src/cursor/cur_version.c
• cd dist && ./s_all completes successfully with no new errors
• Evergreen patch submitted and all unit-test tasks pass on all build variants:

  evergreen patch -p wiredtiger --rt "unit-test" --rv ".*" -f -u -d "WT-17483 verify CCN below threshold and document refactor" -y