ClickDown

- Fixed the 1.15.9 "script ran too long" error in action-button discovery.
- Removed the expensive pairs(_G) scan that tested every global name against
  26 Lua patterns. The new shared Classic UI exposes far more unrelated globals,
  making that old discovery path exceed the client's script watchdog.
- Replaced global scanning with bounded direct lookups for known Blizzard,
  Bartender4, Dominos, ElvUI, and Neuron button-name families.
- Added direct support for the shared ZoneAbilityFrame.SpellButton child.
- Restricted ADDON_LOADED rescans to supported action-bar suites and relevant
  Blizzard action-bar modules instead of reacting to every loaded addon.
- Combat transitions still use the cached native AnyDown/AnyUp registration
  restored in v3.4.3; no global discovery runs when combat starts or ends.
- Renamed the diagnostic counter from "Full scans" to "Discovery passes".