fix(collector): unwrap double-wrapped RFC5424 around bash PROMPT_COMMAND

Honeypot SSH containers run `PROMPT_COMMAND` that calls
`logger --rfc5424 --msgid command -t bash "CMD …"`. The Docker-stdout
reader prepends an outer RFC5424 envelope (HOSTNAME=<decky>,
APP-NAME=1, MSGID=NIL) around that inner syslog line. Both the
collector parser (`parse_rfc5424`) and the correlation parser
(`parse_line`) saw the outer NIL MSGID and emitted `event_type="-"`
for every shell command — which:
  - kept `Attacker.commands` rows missing `command_text`
  - left R0001–R0030 (the pattern rule pack that matches shell
    commands) with no haystack
  - made `decnet.collector.log` show `event written … type=-`
    for the very lines that should be `type=command`

Both parsers now detect the inner-RFC5424 shape (`<TS> <HOST> <APP>
<PROCID> <MSGID> <rest>`) when the outer MSGID is NIL and the SD-arm
is also NIL, and re-extract HOSTNAME / APP-NAME / MSGID / remainder
from the body. The collector parser also recovers the post-SD msg
tail when the SD block isn't `relay@55555` (the bash CMD line carries
a `[timeQuality …]` block) so the kv-fallback can find `src_ip`.

Mirroring tests in tests/collector and tests/correlation pin both
the unwrap and the regression guard for non-double-wrapped lines.

tests/collector/test_parse_rfc5424_double_wrap.py

@@ -0,0 +1,87 @@
+"""Collector parser unwraps double-wrapped RFC5424 lines.
+
+Honeypot SSH containers export a ``PROMPT_COMMAND`` that calls
+``logger --rfc5424 --msgid command -p user.info -t bash "CMD …"``.
+The Docker-stdout reader prepends an outer RFC 5424 envelope around
+that inner syslog line. Outer MSGID is NIL, so without an unwrap step
+every shell command lands as ``event_type="-"`` in the collector
+output and the TTP rule pack never sees it.
+"""
+from __future__ import annotations
+
+from decnet.collector.worker import parse_rfc5424
+
+
+_DOUBLE_WRAPPED_CMD = (
+    "<14>1 2026-05-02T06:22:48.089309+00:00 omega-decky 1 - - - "
+    " 2026-05-02T06:22:48.089286+00:00 SRV-DELTA-77 bash - command "
+    "[timeQuality tzKnown=\"1\" isSynced=\"1\" syncAccuracy=\"326228\"] "
+    "CMD uid=0 user=root src=192.168.1.5 pwd=/root cmd=ls /var/www/html"
+)
+
+
+def test_double_wrapped_bash_cmd_extracts_inner_msgid() -> None:
+    p = parse_rfc5424(_DOUBLE_WRAPPED_CMD)
+    assert p is not None
+    assert p["event_type"] == "command"
+    # decky / service come from the INNER header — not the outer
+    # ``omega-decky`` / ``1`` Docker envelope fields.
+    assert p["decky"] == "SRV-DELTA-77"
+    assert p["service"] == "bash"
+
+
+def test_double_wrapped_bash_cmd_recovers_attacker_ip_from_msg() -> None:
+    p = parse_rfc5424(_DOUBLE_WRAPPED_CMD)
+    assert p is not None
+    assert p["attacker_ip"] == "192.168.1.5"
+
+
+def test_double_wrapped_bash_cmd_preserves_full_msg_body() -> None:
+    p = parse_rfc5424(_DOUBLE_WRAPPED_CMD)
+    assert p is not None
+    # The cmd= value lives at the tail of msg; downstream consumers
+    # (session aggregator, profiler) extract it from there.
+    assert "cmd=ls /var/www/html" in p["msg"]
+
+
+def test_single_wrapped_relay_line_still_parses_unchanged() -> None:
+    """Regression guard: non-double-wrapped lines must keep their shape."""
+    line = (
+        "<134>1 2026-05-02T06:00:25.453826+00:00 omega-decky smtp - "
+        "disconnect [relay@55555 src_ip=\"192.168.1.5\"]"
+    )
+    p = parse_rfc5424(line)
+    assert p is not None
+    assert p["event_type"] == "disconnect"
+    assert p["decky"] == "omega-decky"
+    assert p["service"] == "smtp"
+    assert p["attacker_ip"] == "192.168.1.5"
+
+
+def test_outer_msgid_set_does_not_recurse() -> None:
+    """When outer MSGID is real, leave it alone — no inner-header lookup."""
+    # Synthetic: outer MSGID=auth_attempt, body contains an
+    # accidental inner-shaped substring. We must NOT replace
+    # auth_attempt with anything from inside the body.
+    line = (
+        "<134>1 2026-05-02T06:22:48.089309+00:00 omega-decky auth-helper - "
+        "auth_attempt [relay@55555 username=\"root\" src_ip=\"192.168.1.5\"]"
+    )
+    p = parse_rfc5424(line)
+    assert p is not None
+    assert p["event_type"] == "auth_attempt"
+    assert p["decky"] == "omega-decky"
+    assert p["service"] == "auth-helper"
+
+
+def test_outer_nil_msgid_with_non_inner_body_unchanged() -> None:
+    """NIL-MSGID lines whose body isn't a wrapped RFC5424 line stay NIL."""
+    # The body is plain prose, not a `<TS> <HOST> <APP> <PROCID> <MSGID>` head.
+    line = (
+        "<14>1 2026-05-02T06:22:48.000000+00:00 host app - - - "
+        "Failed password for root from 192.168.1.5 port 42772 ssh2"
+    )
+    p = parse_rfc5424(line)
+    assert p is not None
+    assert p["event_type"] == "-"
+    assert p["attacker_ip"] == "192.168.1.5"