fix: use PR base branch for schema diff check

Author: FL4TLiN3

scripts/check-schema-diff.ts

@@ -7,7 +7,8 @@ const CORE_SCHEMAS_DIR = "packages/core/src/schemas"
 const CHANGESET_DIR = ".changeset"
 async function getChangedSchemaFiles(): Promise<string[]> {
   try {
-    const diff = execSync("git diff --name-only HEAD", { encoding: "utf-8" })
+    const baseBranch = process.env.GITHUB_BASE_REF || "main"
+    const diff = execSync(`git diff --name-only origin/${baseBranch}...HEAD`, { encoding: "utf-8" })
     const changedFiles = diff.split("\n").filter(Boolean)
     return changedFiles.filter((file) => file.startsWith(CORE_SCHEMAS_DIR) && file.endsWith(".ts"))
   } catch {