Added rifle-butt close combat

I added Rifle Butt as an explicit action for an equipped rifle. It uses reach, posture, usable-arm and time-unit checks, deals twelve to eighteen raw damage, and leaves the ammunition count unchanged.

Selecting a normal firing mode restores ranged use. The strike now pivots at the authored grip and reaches forward with the stock; native swing and impact cues accompany it. Hand-contact polish is still open, so this is the working combat action rather than a claim that every animation detail is finished.

“An equipped rifle can strike at close range without spending ammunition, then return to its ranged fire mode.”