Refactor paired execution flow boundaries

shared/verification-snapshot.d.ts

@@ -0,0 +1,8 @@
+export declare const VERIFICATION_SNAPSHOT_EXCLUDE_NAMES: ReadonlySet<string>;
+export declare function isVerificationSnapshotExcludedName(
+  name: string,
+): boolean;
+export declare function computeVerificationSnapshotId(repoDir: string): string;
+export declare function resolveVerificationResponsesDir(
+  hostIpcDir: string,
+): string;