feat(gateway): per-channel model and system prompt overrides (Fixes #1955)

- ChannelOverride + channel_overrides; session /model > channel > global
- Thread/parent lookup; YAML bridge for discord.channel_overrides
- Guard channel_overrides when config lacks platforms (test mocks)
- Add sampiyonyus@gmail.com to AUTHOR_MAP

gateway/run.py

@@ -2343,7 +2343,10 @@ def _get_channel_override(
     Looks up ``channel_overrides`` by ``chat_id``, then ``thread_id``, then
     ``parent_id`` (forum threads / child channels inherit the parent entry).
     """
-    platform_config = config.platforms.get(platform)
+    platforms = getattr(config, "platforms", None)
+    if not platforms:
+        return None
+    platform_config = platforms.get(platform)
     if not platform_config or not platform_config.channel_overrides:
         return None
     overrides = platform_config.channel_overrides

scripts/release.py

@@ -918,6 +918,7 @@ AUTHOR_MAP = {
     "fr@tecompanytea.com": "ifrederico",
     "cdanis@gmail.com": "cdanis",
     "samherring99@gmail.com": "samherring99",
+    "sampiyonyus@gmail.com": "crazywriter1",
     "desaiaum08@gmail.com": "Aum08Desai",
     "shannon.sands.1979@gmail.com": "shannonsands",
     "shannon@nousresearch.com": "shannonsands",