Discord: channel list and presence without the main bot (server-26#225 S5)

A server linked to an org now shows in the node picker while a radio bot the
org may use is in it, even when the DRB server bot is absent or left. Its
voice-channel list is read from that radio bot's cached REST snapshot
(discord_rest.guild_directory, the same snapshot the permission check reads,
so no extra Discord request): inline when no list is stored, in the
background when the list is older than discord_directory_refresh_seconds.
The server bot's own fresh list still wins (back-compat) and its directory
push now drops the server's cached snapshots.

Guards: a server acting only through the unlinked-server fallback org still
needs the server bot; REST never creates a discord_guilds doc, never writes
org_id or bot_present, and never writes onto a server unlinked meanwhile.

Also fixes server-26#251: an interactive start (/join, admin page, web
picker, node discord_join) re-reads a cached "denied" snapshot older than
10 s once before refusing, so "fix it in Discord, then try again" works on
the next try. The reconciler never re-reads (no REST loop).

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

drb-c2-core/app/internal/discord_streams.py

@@ -53,6 +53,7 @@ A retained MQTT message therefore never stores a bot credential on the broker.
 from __future__ import annotations
 
 import asyncio
+import time
 from datetime import datetime, timezone, timedelta
 from typing import Optional
 
@@ -352,14 +353,39 @@ async def check_bots(tokens: dict[str, dict], token_ids: list[str], guild_id: st
             for t in token_ids}
 
 
+# server-26#251: an interactive start (a person pressed Start / ran /join)
+# re-reads a bot's snapshot that says "denied" once it is this old, so a
+# permission fixed in Discord a moment ago is seen without waiting out the
+# cache. The reconciler never does (plan finding 4: no REST loop).
+RECHECK_DENIED_AFTER_SECONDS = 10.0
+
+
 async def _perm_check(*, org_id: str, guild_id: str, channel_id: str, stream_id: str,
-                      preferred_token_id: Optional[str], node_ids: set) -> Optional[dict]:
+                      preferred_token_id: Optional[str], node_ids: set,
+                      recheck_denied: bool = False) -> Optional[dict]:
     if not settings.discord_perm_check_enabled:
         return None
     tokens = {t["token_id"]: t for t in await fstore.collection_list(leases.TOKENS) if t.get("token_id")}
     ids = tokens_to_check(tokens, guild_id=guild_id, org_id=org_id, node_ids=node_ids,
                           exclude_stream_id=stream_id, preferred_token_id=preferred_token_id)
-    return await check_bots(tokens, ids, guild_id, channel_id)
+    snaps = await gather_snapshots(tokens, ids, guild_id)
+
+    def verdict(t: str) -> dict:
+        return evaluate_access(snaps[t], channel_id, bot=tokens[t].get("name") or t) if snaps.get(t) \
+            else _unanswered()
+
+    out = {t: verdict(t) for t in ids}
+    if recheck_denied:
+        now = time.time()
+        stale = [t for t in ids if out[t]["status"] == leases.PERM_DENIED
+                 and now - (getattr(snaps.get(t), "fetched_at", None) or now) >= RECHECK_DENIED_AFTER_SECONDS]
+        if stale:
+            fresh = await gather_snapshots(tokens, stale, guild_id, refresh=True)
+            for t, snap in fresh.items():
+                if snap is not None:     # not answered in time: keep the cached verdict
+                    snaps[t] = snap
+                    out[t] = verdict(t)
+    return out
 
 
 def _channel_ref(perms: Optional[dict], channel_name: Optional[str]) -> str:
@@ -484,6 +510,7 @@ async def start_stream(
     preferred_token_id: Optional[str] = None,
     max_streams: Optional[int] = None,
     stream_id: Optional[str] = None,
+    interactive: bool = False,
 ) -> dict:
     """Put ``system_id`` on a voice channel.
 
@@ -504,6 +531,12 @@ async def start_stream(
     channel first (``_perm_check``; server-26#225). Every entry point — the
     bot's /join, the web picker, the node command and the reconciler —
     comes through here, so none can hand a node a bot Discord will refuse.
+
+    ``interactive``: a person asked for this start (the routes pass True,
+    the reconciler never does). A bot whose cached check says "denied" is
+    then asked again if that answer is more than
+    ``RECHECK_DENIED_AFTER_SECONDS`` old (server-26#251), so "fix it in
+    Discord, then try again" works on the next try.
     """
     if mode not in ("persistent", "adhoc"):
         raise StreamError("bad_mode", "mode must be persistent or adhoc", status=400)
@@ -527,14 +560,14 @@ async def start_stream(
             org_id=org_id, guild_id=guild_id, channel_id=channel_id, system_id=system_id, mode=mode,
             channel_name=channel_name, guild_name=guild_name, created_by=created_by, node_id=node_id,
             preferred_token_id=preferred_token_id, max_streams=max_streams, stream_id=stream_id,
-            existing=existing,
+            existing=existing, interactive=interactive,
         )
 
 
 async def _start_locked(*, org_id: str, guild_id: str, channel_id: str, system_id: str, mode: str,
                         channel_name: Optional[str], guild_name: Optional[str], created_by: Optional[str],
                         node_id: Optional[str], preferred_token_id: Optional[str], max_streams: Optional[int],
-                        stream_id: Optional[str], existing: dict) -> dict:
+                        stream_id: Optional[str], existing: dict, interactive: bool = False) -> dict:
     already_on = False
     if stream_id:
         existing = await fstore.doc_get(STREAMS, stream_id) or existing   # re-read under the lock
@@ -612,7 +645,8 @@ async def _start_locked(*, org_id: str, guild_id: str, channel_id: str, system_i
 
     node_ids = {n["node_id"] for n in candidates}
     perms = await _perm_check(org_id=org_id, guild_id=guild_id, channel_id=channel_id, stream_id=stream_id,
-                              preferred_token_id=preferred_token_id, node_ids=node_ids)
+                              preferred_token_id=preferred_token_id, node_ids=node_ids,
+                              recheck_denied=interactive)
     if perms and any(p.get("status") == "bad_channel" for p in perms.values()):
         raise StreamError("bad_channel", f"{_channel_ref(perms, channel_name)} is not a voice channel. "
                                          "Radio can only play in a voice channel — pick one from the list.",
@@ -638,7 +672,7 @@ async def _start_locked(*, org_id: str, guild_id: str, channel_id: str, system_i
                     # Bots that just turned out to be members get checked too.
                     perms = await _perm_check(org_id=org_id, guild_id=guild_id, channel_id=channel_id,
                                               stream_id=stream_id, preferred_token_id=preferred_token_id,
-                                              node_ids=node_ids)
+                                              node_ids=node_ids, recheck_denied=interactive)
                 res = await leases.lease_for_stream(stream_id, node_id=node["node_id"], org_id=org_id,
                                                     preferred_token_id=preferred_token_id, stream_fields=fields,
                                                     soft_preferred_token_id=soft_pref, perms=perms)