refactor(schema): apply session review decisions (#35793)

packages/schema/src/file-diff.ts

@@ -1,13 +1,23 @@
 export * as FileDiff from "./file-diff.js"
 
 import { Schema } from "effect"
-import { optional } from "./schema.js"
+import { NonNegativeInt, optional } from "./schema.js"
 
 export const Info = Schema.Struct({
-  file: optional(Schema.String),
-  patch: optional(Schema.String),
+  file: Schema.String,
+  patch: Schema.String,
+  additions: NonNegativeInt,
+  deletions: NonNegativeInt,
+  status: Schema.Literals(["added", "deleted", "modified"]),
+}).annotate({ identifier: "FileDiff.Info" })
+export interface Info extends Schema.Schema.Type<typeof Info> {}
+
+/** V1 snapshot and persisted session diff shape. */
+export const LegacyInfo = Schema.Struct({
+  file: Schema.String.pipe(optional),
+  patch: Schema.String.pipe(optional),
   additions: Schema.Finite,
   deletions: Schema.Finite,
-  status: optional(Schema.Literals(["added", "deleted", "modified"])),
-}).annotate({ identifier: "SnapshotFileDiff" })
-export interface Info extends Schema.Schema.Type<typeof Info> {}
+  status: Schema.Literals(["added", "deleted", "modified"]).pipe(optional),
+}).annotate({ identifier: "FileDiff.LegacyInfo" })
+export interface LegacyInfo extends Schema.Schema.Type<typeof LegacyInfo> {}