Add support for Runegraft of the Agile

[czarandy]

Description of the problem being solved:

Runegraft of the Agile causes Elusive's effect to increase for the first 2 seconds before decaying normally, but PoB's average Elusive effect did not account for this growth phase.

This adds parsing for the Runegraft and calculates the time-weighted average when using average elusive calculation mode

Steps taken to verify a working solution:

• Added test coverage for normal and Runegraft Elusive averages.
• Tested increased Elusive effect, removal thresholds, and manual overrides.
• Regenerated ModCache and verified deterministic output.
• Ran the full Busted suite: 296 successes, 0 failures, 0 errors.