fix(source): fix type error in git status source

Handle unknown error type properly by checking if it's an Error instance
before accessing the name property.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: lambdalisue

builtin/source/git_status.ts

@@ -197,7 +197,7 @@ export function gitStatus(
       yield* items;
     } catch (err) {
       // Handle errors gracefully
-      if (err.name === "NotFound") {
+      if (err instanceof Error && err.name === "NotFound") {
         // Git not installed - silently return empty
         return;
       }