Fix comparison ordering to use absolute rank gaps

[ALeonard9]

Summary

• replace percentile-normalized comparison distance with abs(your rank - their rank)
• order biggest gaps from largest raw difference to smallest
• order most aligned from smallest raw difference to largest
• update the overall alignment score to use the average raw rank gap
• update the explanation shown on comparison pages

Regression coverage

• equal ranks such as #14 and #14 produce a zero gap and sort first under Most aligned
• rankings such as #88 and #10 produce a gap of 78 and sort under Biggest gaps
• integration coverage asserts both full orderings

Verification

• full API suite: 791 passed
• Black and Pylint passed
• changed-test pre-push suite passed