feat(feishu): operator-configurable bot admission and mention policy

Add two operator-facing toggles for inbound Feishu admission, enabling
bot-to-bot scenarios such as A2A orchestration and inter-bot
notifications:

  FEISHU_ALLOW_BOTS=none|mentions|all   (default: none)
    Accept messages from other bots. `mentions` requires the peer
    bot to @-mention Hermes; `all` admits every peer-bot message.

  FEISHU_REQUIRE_MENTION=true|false     (default: true)
    Whether group messages must @-mention the bot. Override per-chat
    via `group_rules.<chat_id>.require_mention` in config.yaml.

Defaults preserve prior behavior. Self-echo protection is always on:
when the bot's identity is unresolved (auto-detection failed and
FEISHU_BOT_OPEN_ID unset), peer-bot messages are rejected fail-closed
to avoid feedback loops.

Admitted peer bots bypass the human-user allowlist
(FEISHU_ALLOWED_USERS) to match existing Discord behavior; humans
still need an explicit allowlist entry. yaml feishu.allow_bots is
bridged to the env var so the adapter and gateway auth layer share
one source of truth.

Resolving peer-bot display names requires the
application:bot.basic_info:read scope; without it, peers still route
but appear as their open_id.

Test: tests/gateway/test_feishu_bot_admission.py covers the admission
pipeline, group-policy bot-bypass, hydration, and event-dispatch
plumbing as a parametrized matrix.

Change-Id: I363cccb578c2a5c8b8bf0f0a890c01c89909e256

tests/gateway/test_config.py

@@ -360,6 +360,38 @@ class TestLoadGatewayConfig:
             "C01ABC": "Code review mode",
         }
 
+    def test_bridges_feishu_allow_bots_from_config_yaml_to_env(self, tmp_path, monkeypatch):
+        hermes_home = tmp_path / ".hermes"
+        hermes_home.mkdir()
+        config_path = hermes_home / "config.yaml"
+        config_path.write_text(
+            "feishu:\n  allow_bots: mentions\n",
+            encoding="utf-8",
+        )
+
+        monkeypatch.setenv("HERMES_HOME", str(hermes_home))
+        monkeypatch.delenv("FEISHU_ALLOW_BOTS", raising=False)
+
+        load_gateway_config()
+
+        assert os.environ.get("FEISHU_ALLOW_BOTS") == "mentions"
+
+    def test_feishu_allow_bots_env_takes_precedence_over_config_yaml(self, tmp_path, monkeypatch):
+        hermes_home = tmp_path / ".hermes"
+        hermes_home.mkdir()
+        config_path = hermes_home / "config.yaml"
+        config_path.write_text(
+            "feishu:\n  allow_bots: all\n",
+            encoding="utf-8",
+        )
+
+        monkeypatch.setenv("HERMES_HOME", str(hermes_home))
+        monkeypatch.setenv("FEISHU_ALLOW_BOTS", "none")
+
+        load_gateway_config()
+
+        assert os.environ.get("FEISHU_ALLOW_BOTS") == "none"
+
     def test_invalid_quick_commands_in_config_yaml_are_ignored(self, tmp_path, monkeypatch):
         hermes_home = tmp_path / ".hermes"
         hermes_home.mkdir()