feat: class count configuration with taint fixes

[Rubyj]

Summary

Adds per-class player count configuration so cooldown rows are duplicated based on how many players of that class are in the raid. Also includes a series of taint fixes to ensure the addon does not break the UI during combat.

Changes

• feat: Class count configuration — duplicate cooldown rows per class player count
• fix: Hoist editBoxes and RefreshAllEditBoxes before OnShow so closure can reference them
• fix: Replace taint-causing SetParent/CreateFrame in RebuildUI with safe frame pool
• fix: Defer Settings.OpenToCategory via C_Timer to avoid protected call taint
• fix: Remove programmatic Settings.OpenToCategory (fully protected in Midnight)
• fix: Eliminate taint by removing SetScript in RebuildUI and dummy pool frames; use row.cd indirection
• fix: Load settings before expanding cooldowns to apply custom durations on load
• docs: Add AGENTS.md with AI assistant instructions and taint anti-patterns