S8: main DRB bot optional end to end + owner-flow integration tests (server-26#225)

- Copy: picker, admin Servers/Streams/How-it-works, org Discord card, bot
  /help and the server-limit refusal no longer imply the DRB server bot is
  required; a radio bot alone is enough.
- Admin overview: per-server main_bot_present, radio_bots, linked_via,
  directory_source; Servers tab gets a Bots column.
- discord_web docstring: states the reversed "never calls Discord" rule
  (plan finding 5) and the optional server bot.
- Server bot directory cog: re-push (which drops C2's cached permission
  answers) on overwrite changes, role permission changes and role deletes.
- tests/test_discord_owner_flows.py: one-bot org (BYO bot, owner-set
  preferred, OAuth link, picker, start, reconciler) and full setup (server
  bot + 4 radio bots: placement, shared channel, every refusal explained),
  against a modelled Discord over httpx.MockTransport.
- storage.download_audio removed: no caller on main since #233.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-server-discord-bot/app/commands/directory.py

@@ -4,15 +4,22 @@ Server directory push (server-26#213 item 3).
 The web node page picks a Discord server + voice channel instead of taking raw
 IDs. It needs each server's name and voice channels, and this bot already has
 them in its gateway cache (default intents include ``guilds``), so it pushes
-them to C2 (PUT /discord/guilds/{id}/directory, service key). C2 never calls
-Discord on the browser's behalf and no token reaches the browser.
+them to C2 (PUT /discord/guilds/{id}/directory, service key).
+
+This bot is optional (server-26#225): in a server it is not in, C2 reads the
+same list over Discord REST with a radio bot's token (routers/discord_web.py).
+Where it is present, its push wins while fresh and also tells C2 to drop its
+cached Discord answers for the server, so a permission fixed in Discord shows
+up on the next check instead of after the cache expires. No token ever
+reaches the browser either way.
 
 Pushed: server name, and per voice channel its id, name, category name and
 order. Nothing about members, messages or roles.
 
 When: every server on ready, on join/leave/rename, on any voice-channel or
-category create/delete/update (debounced per server), and a full re-push every
-15 minutes in case C2 missed one (it was down, or redeployed).
+category create/delete/update — including a permission-overwrite change — and
+on a role permission change or role delete (debounced per server), and a full
+re-push every 15 minutes in case C2 missed one (it was down, or redeployed).
 """
 import asyncio
 from typing import Optional
@@ -123,10 +130,22 @@ class DirectorySync(commands.Cog):
 
     @commands.Cog.listener()
     async def on_guild_channel_update(self, before: discord.abc.GuildChannel, after: discord.abc.GuildChannel):
+        # Overwrites too: the push makes C2 drop its cached permission answers
+        # for this server (server-26#225), so "Re-check" sees the fix at once.
         if _relevant(after) and (before.name != after.name or before.position != after.position
-                                 or getattr(before, "category_id", None) != getattr(after, "category_id", None)):
+                                 or getattr(before, "category_id", None) != getattr(after, "category_id", None)
+                                 or before.overwrites != after.overwrites):
             self.schedule(after.guild)
 
+    @commands.Cog.listener()
+    async def on_guild_role_update(self, before: discord.Role, after: discord.Role):
+        if before.permissions != after.permissions:
+            self.schedule(after.guild)
+
+    @commands.Cog.listener()
+    async def on_guild_role_delete(self, role: discord.Role):
+        self.schedule(role.guild)
+
 
 async def setup(bot: commands.Bot):
     await bot.add_cog(DirectorySync(bot))