feat: variables 2.0 state + L0 summary integration

modules/variables/state2/index.js

@@ -0,0 +1,3 @@
+export { applyStateForMessage, clearStateAppliedFor, clearStateAppliedFrom } from './executor.js';
+export { parseStateBlock, extractStateBlocks, computeStateSignature, parseInlineValue } from './parser.js';
+export { generateSemantic } from './semantic.js';