fix(relay): declare explicit relevance policy when require_mention is configured false (#69816)

Companion to gateway-gateway#160 (connector absent-row default flips to
mention-gated / requireAddress=true).

relay_relevance_policy() previously returned None whenever the projected
policy was all-falsy, on the premise that 'the connector's quiet default
already matches'. Once the connector defaults requireAddress to true,
that premise inverts for one case: an agent EXPLICITLY configured with
require_mention: false would stay silent and get mention-gated anyway,
with no way out.

The nothing-to-declare check now keys on 'require_mention is unset'
rather than 'require_mention is falsy': an explicit false IS a
configured knob and is declared to the connector; a genuinely
unconfigured platform still declares nothing and inherits the
connector's default. No wire/contract change.

gateway/relay/__init__.py

@@ -309,7 +309,9 @@ def relay_relevance_policy(platform: Optional[str] = None) -> Optional[dict]:
     the ``{PLATFORM}_*`` env. ``platform`` defaults to the PRIMARY fronted
     platform (back-compat). Returns the generic dict, or None when relay isn't
     configured or the platform exposes no relevance knobs (⇒ the connector's
-    quiet default already matches, so there's nothing to declare).
+    default — mention-gated — applies unchallenged; an EXPLICIT
+    ``require_mention: false`` IS a knob and is declared so the connector
+    doesn't mention-gate an agent configured to free-respond).
     """
     if platform is None:
         platform, _bot_id = relay_platform_identity()
@@ -351,13 +353,18 @@ def relay_relevance_policy(platform: Optional[str] = None) -> Optional[dict]:
     allow_bots_env = os.environ.get(f"{platform.upper()}_ALLOW_BOTS", "").lower().strip()
     allow_other_bots = allow_bots_env in {"mentions", "all"}
 
-    require_address = bool(require_mention) if require_mention is not None else False
-
-    # Nothing non-default to declare ⇒ let the connector keep its quiet default
-    # (matches absence-of-row semantics on the connector side).
-    if not require_address and not free_response and not allow_other_bots:
+    # Nothing CONFIGURED to declare ⇒ let the connector keep its default policy
+    # (mention-gated with agent-thread continuation — matches absence-of-row
+    # semantics on the connector side). NOTE the condition is "require_mention
+    # is unset", NOT "require_mention is falsy": the connector's default is now
+    # requireAddress=true, so an EXPLICIT `require_mention: false` is a
+    # non-default choice that MUST be declared or the connector would
+    # mention-gate an agent configured to free-respond.
+    if require_mention is None and not free_response and not allow_other_bots:
         return None
 
+    require_address = bool(require_mention) if require_mention is not None else False
+
     return {
         "platform": platform,
         "requireAddress": require_address,

tests/gateway/relay/test_relay_policy_send.py

@@ -87,12 +87,44 @@ def test_projection_falls_back_to_top_level_require_mention(monkeypatch):
 
 def test_projection_none_when_all_default(monkeypatch):
     # No require_mention, no free-response, no allow-bots ⇒ nothing to declare
-    # (the connector's quiet default already matches).
+    # (the connector's default — mention-gated — applies).
     monkeypatch.setenv("GATEWAY_RELAY_PLATFORMS", "discord")
     monkeypatch.setattr("gateway.run._load_gateway_config", lambda: {"discord": {}}, raising=False)
     assert relay.relay_relevance_policy() is None
 
 
+def test_projection_declares_explicit_require_mention_false(monkeypatch):
+    # An EXPLICIT `require_mention: false` is a configured (non-default) choice
+    # and MUST be declared: the connector's absent-row default is now
+    # requireAddress=true, so staying silent would mention-gate an agent the
+    # operator configured to free-respond.
+    monkeypatch.setenv("GATEWAY_RELAY_PLATFORMS", "discord")
+    monkeypatch.setattr(
+        "gateway.run._load_gateway_config",
+        lambda: {"discord": {"require_mention": False}},
+        raising=False,
+    )
+    pol = relay.relay_relevance_policy()
+    assert pol == {
+        "platform": "discord",
+        "requireAddress": False,
+        "freeResponseScopes": [],
+        "allowOtherBots": False,
+    }
+
+
+def test_projection_declares_explicit_top_level_require_mention_false(monkeypatch):
+    # Same as above via the bridged top-level key.
+    monkeypatch.setenv("GATEWAY_RELAY_PLATFORMS", "discord")
+    monkeypatch.setattr(
+        "gateway.run._load_gateway_config",
+        lambda: {"require_mention": False},
+        raising=False,
+    )
+    pol = relay.relay_relevance_policy()
+    assert pol is not None and pol["requireAddress"] is False
+
+
 def test_projection_none_when_platform_unresolved(monkeypatch):
     # Default platform "relay" ⇒ no concrete fronted platform ⇒ nothing to project.
     monkeypatch.setattr(