chore(git): ignore prompt.txt and the kigicli.dev worker artifacts

`/prompt.txt` is the one-shot Mac Mini runner-setup prompt. It carries a
Gitea runner registration token once filled in, and a leaked registration
token lets anyone attach a runner to the account and receive our jobs —
including release jobs. Anchored with a leading slash so a legitimately
tracked prompt.txt deeper in the tree would still be versioned.

The .wrangler/ and node_modules/ lines were already sitting uncommitted in
the working tree for the untracked frontend/ worker; they belong in this
same file, so they ride along rather than being split out.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,3 +1,10 @@
 /target
 **/*.rs.bk
 .DS_Store
+
+# frontend/ (kigicli.dev worker)
+.wrangler/
+node_modules/
+
+# Runner-setup prompt; holds a Gitea registration token once filled in.
+/prompt.txt