fix(sync): raise maxBuffer to 100 MiB to prevent silent ENOBUFS crash (#982)

Node's default maxBuffer for execFileSync is 1 MiB. On repos with
60-100K files, `git diff --name-status -M` output easily exceeds this,
causing the sync process to die silently with no error in the log.

Observed at /data/brain (99K files, 62K in git ls-files): sync
consistently died during the rename-detection phase at ~15% through
`buildSyncManifest()`. No stack trace, no error event — just a dead
process. The fix survived 5+ full syncs on the same corpus.

100 MiB is generous but bounded. A 100K-file diff with long paths
tops out around 10-20 MiB in practice.

Co-authored-by: garrytan-agents <garrytan-agents@users.noreply.github.com>

src/commands/sync.ts

@@ -211,10 +211,21 @@ export function buildGitInvocation(repoPath: string, args: string[], configs: st
   return [...cfg, '-C', repoPath, ...args];
 }
 
+/**
+ * Shell out to git with a generous maxBuffer.
+ *
+ * Node's default maxBuffer is 1 MiB.  `git diff --name-status -M` on a
+ * 60–100K file repo easily exceeds that, causing an ENOBUFS crash that
+ * kills the sync process with no error message in the log.
+ *
+ * 100 MiB is generous but still bounded — a 100K-file diff with long
+ * paths tops out around 10–20 MiB in practice.
+ */
 function git(repoPath: string, args: string[], configs: string[] = []): string {
   return execFileSync('git', buildGitInvocation(repoPath, args, configs), {
     encoding: 'utf-8',
     timeout: 30000,
+    maxBuffer: 100 * 1024 * 1024,
   }).trim();
 }