user_input mechanism refactoring.
Balance tune & bug fix

* Marisa, Kogasa, Meirin: their skill effect can choose card now
* Meirin: LoongPunch tune
* SaigyouBranch: can't respond Reject now.
* FlirtingSword: ui_meta can't choose equips now
UserAction: do not be invalid when src or tgt dead.

* Before fix, this interrupts AOE when source dead in progress.
Umbrella: do not block spellcard directly.
THBRAID: Mutant act first in stage1.
THBRAID: exclude ElementalReactorCard
incr ver, welcome msg.