fix(gateway): isinstance-guard string-form 429 error body

When a non-Anthropic provider (e.g. Morpheus proxy) returns a 429 with
`{"error": "Too Many Requests"}` instead of the expected
`{"error": {"type": ...}}` dict, _err_body.json().get("error", {})
returns the raw string and the next .get("type") line crashes with
AttributeError, taking down the message handler.

Guard with isinstance(_err_json, dict) so non-dict error bodies fall
through to the generic rate-limit hint.

Salvaged from PR #2587 by @KiraKatana. The PR's fallback-config
`base_url`/`api_key_env` fix was already implemented independently
on main (run_agent.py:8759-8780) with additional aliases and Ollama
Cloud host handling, so only the gateway guard is cherry-picked.

Co-authored-by: KiraKatana <kira.ops@proton.me>

scripts/release.py

@@ -637,6 +637,7 @@ AUTHOR_MAP = {
     "skmishra1991@gmail.com": "bugkill3r",
     "karamusti912@gmail.com": "MustafaKara7",
     "kira@ariaki.me": "kira-ariaki",
+    "kira.ops@proton.me": "KiraKatana",
     "knopki@duck.com": "knopki",
     "limars874@gmail.com": "limars874",
     "lisicheng168@gmail.com": "lesterli",