fix(kimi): exclude brotli from Accept-Encoding to work around httpx/brotlicffi streaming decode bug (#59556)

httpx's brotlicffi backend (pinned for Discord attachment decoding) fails
on Kimi API's content-encoding: br SSE streaming responses with:

  brotli: decoder process called with data when can_accept_more_data() is False

This surfaces as 'API call failed after 3 retries: Connection error'
on Windows Desktop where the Electron-packaged Python venv includes
brotlicffi (#59556).  DeepSeek and Xiaomi are unaffected — only
moonshot endpoints (api.moonshot.ai, api.moonshot.cn) trigger the bug.

The fix forces Accept-Encoding: gzip so the Kimi API falls back to gzip
compression, which httpx handles reliably on all platforms.  This is the
same workaround already applied in tools/skills_hub.py for sitemap
fetches and the Hermes index download.

Closes associated issues: #28043, #48428

(cherry picked from commit 9c130133b0676138858b73847d1d7c7549339484)

plugins/model-providers/kimi-coding/__init__.py

@@ -13,6 +13,10 @@ _HEADERS = {
     "HTTP-Referer": "https://hermes-agent.nousresearch.com",
     "X-Title": "Hermes Agent",
     "User-Agent": f"HermesAgent/{_HERMES_VERSION}",
+    # Exclude brotli: httpx's brotlicffi backend has a streaming decode bug on
+    # Moonshot's content-encoding: br SSE responses (#28043, #48428, #59556).
+    # gzip sidesteps it while still compressing the transfer.
+    "Accept-Encoding": "gzip",
 }