feat(sync): add Claude home sync parity across providers

src/sync/json-config.ts

@@ -0,0 +1,47 @@
+import path from "path"
+import { pathExists, readJson, writeJsonSecure } from "../utils/files"
+
+type JsonObject = Record<string, unknown>
+
+function isJsonObject(value: unknown): value is JsonObject {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+}
+
+export async function mergeJsonConfigAtKey(options: {
+  configPath: string
+  key: string
+  incoming: Record<string, unknown>
+}): Promise<void> {
+  const { configPath, key, incoming } = options
+  const existing = await readJsonObjectSafe(configPath)
+  const existingEntries = isJsonObject(existing[key]) ? existing[key] : {}
+  const merged = {
+    ...existing,
+    [key]: {
+      ...existingEntries,
+      ...incoming,
+    },
+  }
+
+  await writeJsonSecure(configPath, merged)
+}
+
+async function readJsonObjectSafe(configPath: string): Promise<JsonObject> {
+  if (!(await pathExists(configPath))) {
+    return {}
+  }
+
+  try {
+    const parsed = await readJson<unknown>(configPath)
+    if (isJsonObject(parsed)) {
+      return parsed
+    }
+  } catch {
+    // Fall through to warning and replacement.
+  }
+
+  console.warn(
+    `Warning: existing ${path.basename(configPath)} could not be parsed and will be replaced.`,
+  )
+  return {}
+}