Implement main-thread Camino sessions and synchronous CRDT editing

grammar/QuixosCapability.g4

@@ -189,18 +189,22 @@ fragmentVariable : identifier TO identifier SEMI;
 
 packageOperationExport
   : OPERATION identifier typeParameters? ID stringLiteral COLON valueType ARROW valueType
-    MODE operationMode executionClause? eventClause? RECEIVER receiverRequirement dependencyBlock? acceptanceClause? SEMI
+    MODE operationMode executionClause? eventClause? RECEIVER receiverRequirement dependencyBlock? preparationClause? acceptanceClause? SEMI
   ;
 
 packageFunctionExport
   : FUNCTION identifier typeParameters? ID stringLiteral COLON valueType ARROW valueType
-    executionClause? dependencyBlock? acceptanceClause? SEMI
+    executionClause? dependencyBlock? preparationClause? acceptanceClause? SEMI
   ;
 
 acceptanceClause
   : ACCEPT USING identifier
   ;
 
+preparationClause
+  : PREPARES CREATION identifier USING stringLiteral
+  ;
+
 executionClause
   : EXECUTION REMOTE
   | EXECUTION (SNAPSHOT | TRANSACTION) TARGETS LBRACK identifierList RBRACK
@@ -418,6 +422,7 @@ valueType
   | OPTIONAL LT valueType GT
   | LIST LT valueType GT
   | RECORD LBRACE recordField* RBRACE
+  | VARIANT ID stringLiteral LBRACE variantCase+ RBRACE
   | identifier typeArguments?
   ;
 
@@ -425,6 +430,10 @@ recordField
   : identifier COLON valueType SEMI
   ;
 
+variantCase
+  : identifier ID stringLiteral COLON valueType SEMI
+  ;
+
 scalarType
   : BOOL
   | BYTES
@@ -517,6 +526,8 @@ PRESENTATION: 'presentation';
 SUBJECT: 'subject';
 FOR: 'for';
 CREATION: 'creation';
+VARIANT: 'variant';
+PREPARES: 'prepares';
 INITIALIZE: 'initialize';
 WORKSPACE: 'workspace';
 EXECUTION: 'execution';