[Bug]: Thunder Clap missing AP coefficient (TBC empirical 12% AP)

[Xerrion]

Problem

Data/SpellData_Warrior.lua Thunder Clap (spellID 6343 and ranks) currently stores only flat damage with no apCoefficient field. The engine's melee-direct path (Engine/SpellCalc.lua ComputeMeleeDirect Type-2) supports apCoefficient but Thunder Clap doesn't declare one, so the spell's damage is reported as flat-rank only and ignores attack power scaling entirely.

Empirical TBC value

WoWWiki Attack_power_coefficient archive (Warrior > Arms section) lists Thunder Clap as scaling at 12% AP (apCoefficient = 0.12).

Expected fix

Add apCoefficient = 0.12 to the Thunder Clap entry in Data/SpellData_Warrior.lua. With AP=2000 this contributes a 240 damage bonus to a flat ~300 damage rank, bringing displayed values in line with empirical TBC behavior.

Discovery context

Found during the AoE coefficient audit for #46 but deliberately excluded from that PR per scope discipline (Thunder Clap is a melee AP correction, not an AoE penalty correction). Filing as separate issue for clean tracking.

Acceptance criteria

• All Thunder Clap ranks declare apCoefficient = 0.12.
• A regression test in tests/ pins the new value and asserts Pipeline.Calculate produces the expected min + AP * 0.12 result.
• Source citation comment added.
• luacheck . clean, busted --verbose passes.

Source

• WoWWiki Attack_power_coefficient archive (Warrior > Arms table)