feat(panel): lay a delivery's log lines out as a table

The lines came out as one block of preformatted text, which is what the
system log page does with a tail of mail.log — right there, where the
lines are unrelated to each other and the block is the log itself. Here
they are one message's six or seven lines, and what is read off them is
the pace: the second between the connection and the banner, the ten
between DATA and the reply. Run together, every line began with a
different-width stamp and none of those numbers lined up.

So they are two columns now, when and what, the same shape the send log
itself has. logtail.SplitTimestamp takes the stamp off the head of a
line: postlogd's format, which is what this server writes, and syslog's
traditional one for a deployment that routes the log through syslogd
instead. The stamp loses its microseconds and its offset — five decimal
places are the widest part of the column and the least worth reading —
but is not converted, so the page shows the log's own wall clock rather
than a claim about which zone it was in.

A line whose head is not a stamp either parser recognises keeps its whole
text in the second column and leaves the first empty. The format is the
log's, not ours; a line we cannot split is a line we must not drop, and
the test says so.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/web/handlers_monitor.go

@@ -85,7 +85,7 @@ func (s *Server) handleDelivery(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	row.Subject = mailhdr.DecodeSubject(row.Subject)
-	lines, logNote := s.deliveryLog(row)
+	logRows, logNote := s.deliveryLog(row)
 	s.render(w, http.StatusOK, "delivery", map[string]any{
 		"Title":  "SelfPost — delivery",
 		"User":   currentUser(r),
@@ -97,8 +97,8 @@ func (s *Server) handleDelivery(w http.ResponseWriter, r *http.Request) {
 		"Events": deliveryEvents(row),
 		// The mail.log lines for this message, and — when there are none — the
 		// reason, which is a normal outcome rather than a failure.
-		"LogLines": lines,
-		"LogNote":  logNote,
+		"LogRows": logRows,
+		"LogNote": logNote,
 		// Where the row came from, so "Back" returns to the page and filters
 		// the operator was looking at rather than the top of an unfiltered log.
 		"BackURL": deliveriesBackURL(r),
@@ -207,13 +207,23 @@ func deliveryEvents(row store.SendLogRow) []deliveryEvent {
 	}
 }
 
-// deliveryLog reads the mail.log lines Postfix wrote about one message. The
-// second return value is what to say when there are none: every reason for an
-// empty result here is an ordinary one — the message never reached the queue,
-// or its lines have aged out of the log — so none of them is an error on the
-// page. Only a log that cannot be read at all is reported as a fault, and that
-// one is logged for the operator as well.
-func (s *Server) deliveryLog(row store.SendLogRow) ([]string, string) {
+// deliveryLogRow is one mail.log line split for the table on the delivery
+// page: when it was written, and what it says. Time is empty for a line whose
+// head is not a timestamp the log format recognises — the line still shows, in
+// full, under Message.
+type deliveryLogRow struct {
+	Time string
+	Text string
+}
+
+// deliveryLog reads the mail.log lines Postfix wrote about one message and
+// splits each into the two columns the page shows it in. The second return
+// value is what to say when there are none: every reason for an empty result
+// here is an ordinary one — the message never reached the queue, or its lines
+// have aged out of the log — so none of them is an error on the page. Only a
+// log that cannot be read at all is reported as a fault, and that one is
+// logged for the operator as well.
+func (s *Server) deliveryLog(row store.SendLogRow) ([]deliveryLogRow, string) {
 	if row.QueueID == "" {
 		return nil, "This message never reached the queue, so Postfix wrote no delivery lines for it."
 	}
@@ -228,7 +238,12 @@ func (s *Server) deliveryLog(row store.SendLogRow) ([]string, string) {
 		// left to show is the normal end state, not a fault.
 		return nil, "Nothing for this queue id in the current mail log. Its lines have most likely been rotated away."
 	}
-	return lines, ""
+	out := make([]deliveryLogRow, len(lines))
+	for i, line := range lines {
+		stamp, rest := logtail.SplitTimestamp(line)
+		out[i] = deliveryLogRow{Time: stamp, Text: rest}
+	}
+	return out, ""
 }
 
 // deliveriesBackURL rebuilds the delivery-log URL a detail page was opened