New campaign/encounter ruleset toggle: 5e (default, unchanged) vs generic.
Generic mode:
- No death saves (deathSave/stabilize throw)
- Negative HP allowed (no clamp at 0)
- <=0 HP = status 'down' (no pips, no unconscious auto-condition)
- Monster death = dead + inactive (same as 5e)
- markDead button: DM sets dead manually (both modes)
- revive: dead->conscious (generic), dead->stable (5e)
5e mode: zero behavior change.
shared/turn.js:
- applyHpChangeGeneric: negative HP, down status, no death-save logic
- markDead: status dead, monster auto-inactive
- reviveParticipant: ruleset-aware (generic=conscious, 5e=stable)
- deathSave/stabilize: throw in generic
- expandUndo: mark_dead case added
UI (src/App.js):
- CreateCampaignForm + CreateEncounterForm: ruleset radio toggle
- handleCreateCampaign/handleCreateEncounter: store ruleset field
- EncounterManager: fetch campaignDoc for default ruleset inheritance
- DM participant: down/dead labels, Mark Dead button (generic), Revive both
- death-save pips/buttons gated 5e-only
- DisplayView: down label, generic status derivation
Tests: 15 generic cases (turn.generic.test.js). 186 shared total.
