feat(prompt): implement prompt injection slice 1

src/index.ts

@@ -23,3 +23,15 @@ export {
 } from "./directory-model.js";
 export { populateRoutingMetadata } from "./routing-metadata.js";
 export { retrieveContext } from "./retrieve.js";
+export {
+	buildRootPairBlock,
+	hasRootPairMarker,
+	buildPreInitHint,
+	computeInjectionBudget,
+	modeAllowsPreInitHint,
+	modeAllowsInjection,
+	modeRequiresProtocolPath,
+	ROOT_PAIR_START_MARKER,
+	ROOT_PAIR_END_MARKER,
+	TRUST_BOUNDARY_TEXT,
+} from "./prompt-injection.js";