test: kill act env warnings + remove debug console noise

Root cause: mock _notify cb fires during waitFor poll, but testing-library
asyncWrapper flips IS_REACT_ACT_ENVIRONMENT=false. Raw react act() then
warns 'not configured to support act' (146 warnings).

Fix: _notify sets globalThis.IS_REACT_ACT_ENVIRONMENT=true around act(),
restores after. setupTests sets flag globally. Both together = 0 warnings.

Also:
- Remove 4 debug console.log from App.js (encounter start/end, drag, add chars)
- Remove always-fires scenario summary console.log
- Add fastWaitFor helper (5ms poll) to testHelpers
- Swap scenario waitFor -> fastWaitFor

Tests: 77 pass / 0 fail / 0 warnings / 0 console noise.

src/App.js

@@ -928,7 +928,6 @@ function ParticipantManager({ encounter, encounterPath, campaignCharacters }) {
       await storage.updateDoc(encounterPath, {
         participants: [...participants, ...newParticipants]
       });
-      console.log(`Added ${newParticipants.length} characters to the encounter.`);
     } catch (err) {
       console.error("Error adding all campaign characters:", err);
       alert("Failed to add all characters. Please try again.");
@@ -1234,7 +1233,6 @@ function ParticipantManager({ encounter, encounterPath, campaignCharacters }) {
     const targetItem = currentParticipants[targetIndex];
 
     if (draggedItem.initiative !== targetItem.initiative) {
-      console.log("Drag-drop only allowed for participants with same initiative.");
       setDraggedItemId(null);
       return;
     }
@@ -1720,7 +1718,6 @@ function InitiativeControls({ campaignId, encounter, encounterPath }) {
           turnOrderIds: [...(encounter.turnOrderIds || [])],
         },
       });
-      console.log("Encounter started and set as active display.");
     } catch (err) {
       console.error("Error starting encounter:", err);
       alert("Failed to start encounter. Please try again.");
@@ -1851,7 +1848,6 @@ function InitiativeControls({ campaignId, encounter, encounterPath }) {
           turnOrderIds: [...(encounter.turnOrderIds || [])],
         },
       });
-      console.log("Encounter ended and deactivated from Player Display.");
     } catch (err) {
       console.error("Error ending encounter:", err);
     }