fix: Signal adapter parity pass — integration gaps, clawdbot features, env var simplification

Integration gaps fixed (7 files missing Signal):
- cron/scheduler.py: Signal in platform_map (cron delivery was broken)
- agent/prompt_builder.py: PLATFORM_HINTS for Signal (agent knows it's on Signal)
- toolsets.py: hermes-signal toolset + added to hermes-gateway composite
- hermes_cli/status.py: Signal + Slack in platform status display
- tools/send_message_tool.py: Signal example in target description
- tools/cronjob_tools.py: Signal in delivery option docs + schema
- gateway/channel_directory.py: Signal in session-based channel discovery

Clawdbot parity features added to signal.py:
- Self-message filtering: prevents reply loops by checking sender != account
- SyncMessage filtering: ignores sync envelopes (sent transcripts, read receipts)
- Edit message support: reads dataMessage from editMessage envelope
- Mention rendering: replaces \uFFFC placeholders with @identifier text
- Jitter in SSE reconnection backoff (20% randomization, prevents thundering herd)

Env var simplification (7 → 4):
- Removed SIGNAL_DM_POLICY (DM auth follows standard platform pattern via
  SIGNAL_ALLOWED_USERS + DM pairing, same as Telegram/Discord)
- Removed SIGNAL_GROUP_POLICY (derived from SIGNAL_GROUP_ALLOWED_USERS:
  not set = disabled, set with IDs = allowlist, set with * = open)
- Removed SIGNAL_DEBUG (was setting root logger, removed entirely)
- Remaining: SIGNAL_HTTP_URL, SIGNAL_ACCOUNT (required),
  SIGNAL_ALLOWED_USERS, SIGNAL_GROUP_ALLOWED_USERS (optional)

Updated all docs (website, AGENTS.md, signal.md) to match.

tests/gateway/test_signal.py

@@ -23,8 +23,6 @@ class TestSignalConfigLoading:
     def test_apply_env_overrides_signal(self, monkeypatch):
         monkeypatch.setenv("SIGNAL_HTTP_URL", "http://localhost:9090")
         monkeypatch.setenv("SIGNAL_ACCOUNT", "+15551234567")
-        monkeypatch.setenv("SIGNAL_DM_POLICY", "open")
-        monkeypatch.setenv("SIGNAL_GROUP_POLICY", "allowlist")
 
         from gateway.config import GatewayConfig, _apply_env_overrides
         config = GatewayConfig()
@@ -35,8 +33,6 @@ class TestSignalConfigLoading:
         assert sc.enabled is True
         assert sc.extra["http_url"] == "http://localhost:9090"
         assert sc.extra["account"] == "+15551234567"
-        assert sc.extra["dm_policy"] == "open"
-        assert sc.extra["group_policy"] == "allowlist"
 
     def test_signal_not_loaded_without_both_vars(self, monkeypatch):
         monkeypatch.setenv("SIGNAL_HTTP_URL", "http://localhost:9090")
@@ -71,49 +67,44 @@ class TestSignalAdapterInit:
         config.extra = {
             "http_url": "http://localhost:8080",
             "account": "+15551234567",
-            "dm_policy": "pairing",
-            "group_policy": "disabled",
             **extra,
         }
         return config
 
     def test_init_parses_config(self, monkeypatch):
-        monkeypatch.setenv("SIGNAL_ALLOWED_USERS", "+15559876543,+15551111111")
         monkeypatch.setenv("SIGNAL_GROUP_ALLOWED_USERS", "group123,group456")
-        monkeypatch.delenv("SIGNAL_DEBUG", raising=False)
 
         from gateway.platforms.signal import SignalAdapter
         adapter = SignalAdapter(self._make_config())
 
         assert adapter.http_url == "http://localhost:8080"
         assert adapter.account == "+15551234567"
-        assert adapter.dm_policy == "pairing"
-        assert adapter.group_policy == "disabled"
-        assert "+15559876543" in adapter.allowed_users
-        assert "+15551111111" in adapter.allowed_users
         assert "group123" in adapter.group_allow_from
 
     def test_init_empty_allowlist(self, monkeypatch):
-        monkeypatch.setenv("SIGNAL_ALLOWED_USERS", "")
         monkeypatch.setenv("SIGNAL_GROUP_ALLOWED_USERS", "")
-        monkeypatch.delenv("SIGNAL_DEBUG", raising=False)
 
         from gateway.platforms.signal import SignalAdapter
         adapter = SignalAdapter(self._make_config())
 
-        assert len(adapter.allowed_users) == 0
         assert len(adapter.group_allow_from) == 0
 
     def test_init_strips_trailing_slash(self, monkeypatch):
-        monkeypatch.setenv("SIGNAL_ALLOWED_USERS", "")
         monkeypatch.setenv("SIGNAL_GROUP_ALLOWED_USERS", "")
-        monkeypatch.delenv("SIGNAL_DEBUG", raising=False)
 
         from gateway.platforms.signal import SignalAdapter
         adapter = SignalAdapter(self._make_config(http_url="http://localhost:8080/"))
 
         assert adapter.http_url == "http://localhost:8080"
 
+    def test_self_message_filtering(self, monkeypatch):
+        monkeypatch.setenv("SIGNAL_GROUP_ALLOWED_USERS", "")
+
+        from gateway.platforms.signal import SignalAdapter
+        adapter = SignalAdapter(self._make_config())
+
+        assert adapter._account_normalized == "+15551234567"
+
 
 class TestSignalHelpers:
     def test_redact_phone_long(self):
@@ -177,6 +168,20 @@ class TestSignalHelpers:
         monkeypatch.setenv("SIGNAL_ACCOUNT", "+15551234567")
         assert check_signal_requirements() is True
 
+    def test_render_mentions(self):
+        from gateway.platforms.signal import _render_mentions
+        text = "Hello \uFFFC, how are you?"
+        mentions = [{"start": 6, "length": 1, "number": "+15559999999"}]
+        result = _render_mentions(text, mentions)
+        assert "@+15559999999" in result
+        assert "\uFFFC" not in result
+
+    def test_render_mentions_no_mentions(self):
+        from gateway.platforms.signal import _render_mentions
+        text = "Hello world"
+        result = _render_mentions(text, [])
+        assert result == "Hello world"
+
     def test_check_requirements_missing(self, monkeypatch):
         from gateway.platforms.signal import check_signal_requirements
         monkeypatch.delenv("SIGNAL_HTTP_URL", raising=False)