Fix: forward env parameter through gitCommand to VcsProcess

The execute method in GitVcsDriver and the gitCommand helper were not
forwarding the env field from the input to process.run. This caused
CheckpointStore.captureCheckpoint's GIT_INDEX_FILE, GIT_AUTHOR_*, and
GIT_COMMITTER_* environment variables to be silently dropped, resulting
in checkpoint operations mutating the user's real staging area instead
of an isolated temporary index.

Author: cursoragent

apps/server/src/vcs/GitVcsDriver.ts

@@ -257,6 +257,7 @@ const gitCommand = (
   args: ReadonlyArray<string>,
   options?: {
     readonly stdin?: string;
+    readonly env?: NodeJS.ProcessEnv;
     readonly allowNonZeroExit?: boolean;
     readonly timeoutMs?: number;
     readonly maxOutputBytes?: number;
@@ -269,6 +270,7 @@ const gitCommand = (
     args,
     cwd,
     ...(options?.stdin !== undefined ? { stdin: options.stdin } : {}),
+    ...(options?.env !== undefined ? { env: options.env } : {}),
     ...(options?.allowNonZeroExit !== undefined
       ? { allowNonZeroExit: options.allowNonZeroExit }
       : {}),
@@ -305,6 +307,7 @@ export const makeVcsDriverShape = Effect.fn("makeGitVcsDriverShape")(function* (
   const execute: VcsDriverShape["execute"] = (input) =>
     gitCommand(process, input.operation, input.cwd, input.args, {
       ...(input.stdin !== undefined ? { stdin: input.stdin } : {}),
+      ...(input.env !== undefined ? { env: input.env } : {}),
       ...(input.allowNonZeroExit !== undefined ? { allowNonZeroExit: input.allowNonZeroExit } : {}),
       ...(input.timeoutMs !== undefined ? { timeoutMs: input.timeoutMs } : {}),
       ...(input.maxOutputBytes !== undefined ? { maxOutputBytes: input.maxOutputBytes } : {}),