S7: OAuth start/options accept system_id; Discord picker QA fixes (server-26#225, #256 #257 #258)

- discord_oauth: POST /discord/oauth/start and GET /options take an optional
  system_id. The system must be the org's own or shared (another org's or
  unknown = 404). Its preferred bot is strict: one that can't connect is a
  404, never a quiet swap to Automatic. No preference = the usual order.
  The picker's "bot for a system" now always sends system_id.
- #257: _channel_state gives a bot whose token Discord rejected its own
  "invalid" state; the picker shows "Radio bot needs replacing" with no
  invite links, instead of "No radio bot".
- #256: Start no longer stays disabled on "Needs fix". It re-checks with
  Discord first (refresh=1) and starts only if the fresh answer allows it.
  "Not a voice channel" still disables Start.
- #258: own tooltip for "Not a voice channel"; "platform admin" -> "DRB
  support"; PreferredBotsCard says plainly that adding your own bot isn't
  self-serve (no support address exists yet, see #47), and a load failure
  gets a plain message + Try again instead of the raw C2 error.

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

drb-c2-core/tests/test_discord_oauth.py

@@ -187,6 +187,58 @@ async def test_preferred_bot_for_the_nodes_system_wins(fs):
     assert e.value.status_code == 404
 
 
+async def test_system_id_invites_that_systems_preferred_bot(fs):
+    """The S7 picker's "bot for a system" choice: a platform-pinned pool bot
+    is invited by system_id, never quietly swapped for Automatic."""
+    fs.put("systems", "s1", {"system_id": "s1", "org_id": "org-a", "preferred_token_id": "pool-1"})
+    out = await router.oauth_options(node_id=None, token_id=None, org_id=None, decoded=OWNER_A, system_id="s1")
+    assert out["bot"] == {"name": "DRB Radio 1", "reason": "preferred", "own_bot": False}
+    out, q = await _start(system_id="s1", return_to="/settings")
+    assert q["client_id"] == "201" and out["bot"]["reason"] == "preferred"
+    assert _audit(fs, "discord.oauth.start")[-1]["details"]["system_id"] == "s1"
+    # a shared system (no org_id) serves every org, as on the node path
+    fs.put("systems", "shared", {"system_id": "shared", "org_id": None, "preferred_token_id": "pool-1"})
+    out = await router.oauth_options(node_id=None, token_id=None, org_id=None, decoded=OWNER_B,
+                                     system_id="shared")
+    assert out["bot"]["name"] == "DRB Radio 1"
+    # system_id outranks node_id
+    fs.put("nodes", "n1", {"node_id": "n1", "org_id": "org-a", "assigned_system_id": "s2"})
+    fs.put("systems", "s2", {"system_id": "s2", "org_id": "org-a", "preferred_token_id": "own-a"})
+    out = await router.oauth_options(node_id="n1", token_id=None, org_id=None, decoded=OWNER_A, system_id="s1")
+    assert out["bot"]["name"] == "DRB Radio 1"
+
+
+async def test_system_id_of_another_org_or_unknown_is_404(fs):
+    fs.put("systems", "sb", {"system_id": "sb", "org_id": "org-b", "preferred_token_id": "pool-1"})
+    for sid in ("sb", "nope"):
+        with pytest.raises(HTTPException) as e:
+            await router.oauth_options(node_id=None, token_id=None, org_id=None, decoded=OWNER_A, system_id=sid)
+        assert e.value.status_code == 404 and e.value.detail == "System not found."
+        with pytest.raises(HTTPException) as e:
+            await _start(system_id=sid)
+        assert e.value.status_code == 404
+    assert not _audit(fs, "discord.oauth.start")
+    # a platform admin acting for org-b may use it
+    out = await router.oauth_options(node_id=None, token_id=None, org_id="org-b", decoded=ADMIN, system_id="sb")
+    assert out["bot"]["name"] == "DRB Radio 1"
+
+
+async def test_system_id_whose_bot_cannot_connect_is_404_not_a_swap(fs):
+    # pool-2 is at the cap; another org's bot pinned (bad data); no secret
+    fs.put("systems", "s1", {"system_id": "s1", "org_id": "org-a", "preferred_token_id": "pool-2"})
+    fs.put("systems", "s2", {"system_id": "s2", "org_id": "org-a", "preferred_token_id": "own-b"})
+    fs.put("systems", "s3", {"system_id": "s3", "org_id": "org-a", "preferred_token_id": "pool-1"})
+    fs.data[oauth.OAUTH].pop("pool-1")
+    for sid in ("s1", "s2", "s3"):
+        with pytest.raises(HTTPException) as e:
+            await router.oauth_options(node_id=None, token_id=None, org_id=None, decoded=OWNER_A, system_id=sid)
+        assert e.value.status_code == 404 and "Harbor" not in str(e.value.detail)
+    # no preferred bot at all: the usual order (org's own bot first)
+    fs.put("systems", "s4", {"system_id": "s4", "org_id": "org-a"})
+    out = await router.oauth_options(node_id=None, token_id=None, org_id=None, decoded=OWNER_A, system_id="s4")
+    assert out["bot"]["reason"] == "org_bot"
+
+
 async def test_explicit_bot_must_be_usable_by_the_org(fs):
     out = await router.oauth_options(node_id=None, token_id="pool-1", org_id=None, decoded=OWNER_A)
     assert out["bot"]["reason"] == "chosen"