Pass env to execFileSync git calls (#1151)

Bun's execFileSync without an explicit env option spawns with the process
startup environment, dropping runtime process.env mutations. The credential
helper reads GH_TOKEN which is set at runtime, so git fetch in the
restore-config path failed with empty password.

Fixes #1139

🏠 Remote-Dev: homespace

src/github/operations/branch.ts

@@ -118,7 +118,7 @@ export function validateBranchName(branchName: string): void {
  * @param args - Git command arguments (e.g., ["checkout", "branch-name"])
  */
 function execGit(args: string[]): void {
-  execFileSync("git", args, { stdio: "inherit" });
+  execFileSync("git", args, { stdio: "inherit", env: process.env });
 }
 
 export type BranchInfo = {

src/github/operations/restore-config.ts

@@ -48,6 +48,7 @@ export function restoreConfigFromBase(baseBranch: string): void {
   // caller sees a clean error.
   execFileSync("git", ["fetch", "origin", baseBranch, "--depth=1"], {
     stdio: "inherit",
+    env: process.env,
   });
 
   // Delete PR-controlled versions. If the restore below fails for a given path,