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-c2-core/app/routers/discord.py

@@ -269,6 +269,11 @@ async def admin_overview(_: dict = Depends(require_admin_token)):
     Radio bots come from ``GET /tokens``; no token string is returned here.
     Discord user ids (``created_by_discord_id``) and the linking admin's uid
     are deliberately left out.
+
+    Per server, ``main_bot_present`` (the DRB server bot — optional since
+    server-26#225: True/False as it last reported, None = never heard from it
+    there) and ``radio_bots`` (names of radio bots Discord last said are in
+    it). A server with radio bots and no server bot is a normal setup.
     """
     links = {str(g.get("guild_id")): g for g in await fstore.collection_list(streams.GUILDS)
              if g.get("guild_id")}
@@ -284,6 +289,11 @@ async def admin_overview(_: dict = Depends(require_admin_token)):
             continue  # removed from DRB (DELETE /discord/guilds/{id}); re-listed if it gets a channel again
         guilds[gid] = {"guild_id": gid, "guild_name": link.get("guild_name"), "linked": bool(link.get("org_id")),
                        "org_id": link.get("org_id"), "linked_at": link.get("linked_at"),
+                       "linked_via": link.get("linked_via"),
+                       # The DRB server bot is optional (server-26#225 S8): True/False
+                       # = it said it is / is not in the server, None = never heard.
+                       "main_bot_present": link.get("bot_present"),
+                       "directory_source": link.get("directory_source"),
                        # Explicitly unlinked servers get no fallback org (mirrors
                        # streams.resolve_guild_org once server-26#218 lands).
                        "_no_fallback": bool(link.get("unlinked_at"))}
@@ -291,7 +301,8 @@ async def admin_overview(_: dict = Depends(require_admin_token)):
     for s in all_streams:
         gid = str(s.get("guild_id") or leases.guild_of(s.get("stream_id") or ""))
         g = guilds.setdefault(gid, {"guild_id": gid, "guild_name": None, "linked": False,
-                                    "org_id": None, "linked_at": None})
+                                    "org_id": None, "linked_at": None, "linked_via": None,
+                                    "main_bot_present": None, "directory_source": None})
         if s.get("guild_name") and not g.get("guild_name"):
             g["guild_name"] = s["guild_name"]
         node = nodes.get(s.get("node_id")) or {}
@@ -305,6 +316,11 @@ async def admin_overview(_: dict = Depends(require_admin_token)):
         g["acting_org_id"] = acting
         g["acting_org_name"] = (orgs.get(acting) or {}).get("name") if acting else None
         g["live_streams"] = sum(1 for r in rows if r.get("guild_id") == g["guild_id"] and r.get("desired") == "on")
+        # Radio bots Discord last said are in the server (names only). Any one
+        # of them is enough to list channels, check permissions and stream.
+        g["radio_bots"] = sorted(str(t.get("name") or tid) for tid, t in tokens.items()
+                                 if t.get("valid") is not False and isinstance(t.get("guild_ids"), list)
+                                 and g["guild_id"] in t["guild_ids"])
 
     # Streams sharing a voice channel sit together, oldest first.
     rows.sort(key=lambda r: (0 if r.get("desired") == "on" else 1, r.get("guild_name") or r.get("guild_id") or "",

drb-c2-core/app/routers/discord_web.py

@@ -21,9 +21,20 @@ Where the directory comes from (server-26#225 S5 — the main bot is optional):
     stored list is missing (inline, inside the permission-check time budget)
     or older than ``discord_directory_refresh_seconds`` (in the background).
 
-So C2 does call Discord when a signed-in user opens the picker — with a
-radio bot's token, for a server already linked to the caller's org, through
-the rate-limited, cached client. No token string ever reaches the browser.
+This reverses the old rule "C2 never calls Discord on the browser's behalf"
+on purpose (server-26#225 plan finding 5): C2 does call Discord when a
+signed-in user opens the picker, presses Start or Re-check — with a radio
+bot's token, only for a server already linked to the caller's org, through
+discord_rest's rate-limited, cached, breaker-guarded client (refresh=1 at
+most once per 10 s per user and server). No token string ever reaches the
+browser, and REST answers never create or re-link a ``discord_guilds`` doc.
+
+The DRB server bot is optional end to end (server-26#225 S8). One radio bot
+in the server is enough to link it (per-bot OAuth, routers/discord_oauth.py),
+list its voice channels (here), check permissions (routers/discord_checks.py)
+and stream (streams.start_stream). The server bot adds its slash commands
+(/join, /leave, /status, /drb link) and a gateway-fed channel list; every
+path it uses keeps working.
 
 Which servers an org sees (``_org_guilds``):