Add --no-optional-locks to prevent stale index.lock files (#63)

Prevents orphaned .git/index.lock files observed when running git status
from Claude Code's statusLine.

src/git.ts

@@ -43,7 +43,7 @@ export async function getGitStatus(cwd?: string): Promise<GitStatus | null> {
     try {
       const { stdout: statusOut } = await execFileAsync(
         'git',
-        ['status', '--porcelain'],
+        ['status', '--porcelain', '--no-optional-locks'],
         { cwd, timeout: 1000, encoding: 'utf8' }
       );
       isDirty = statusOut.trim().length > 0;