fix(ui): render TUI log lines on their own rows, with colors and a small header (#5324)

- log lines shown under the TUI were glued onto the last UI row, and the last row could get erased (and overwritten by the report) when the TUI exits. Fixed in `bubbly` v0.2.2
- log colors were lost because the logger latched its TTY check on the first entry, which went to the TUI footer buffer. `go-logger` v0.2.0 checks per entry and supports `TerminalWriter`, which the footer writer now implements (`NO_COLOR` is still honored)
- log lines under the TUI get a dim `Logs (non-fatal, see -v for more):` title with a branch pointing at the first entry, so it's clear what the trailing lines are

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

cmd/syft/internal/ui/ui.go

@@ -1,6 +1,7 @@
 package ui
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -8,6 +9,7 @@ import (
 	"time"
 
 	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
 	"github.com/wagoodman/go-partybus"
 
 	"github.com/anchore/bubbly"
@@ -52,7 +54,7 @@ func New(out io.Writer, quiet bool, handlers ...bubbly.EventHandler) *UI {
 func (m *UI) Setup(subscription partybus.Unsubscribable) error {
 	// we still want to collect log messages, however, we also the logger shouldn't write to the screen directly
 	if logWrapper, ok := log.Get().(logger.Controller); ok {
-		logWrapper.SetOutput(m.frame.(*frame.Frame).Footer())
+		logWrapper.SetOutput(&logFooter{w: m.frame.(*frame.Frame).Footer()})
 	}
 
 	m.subscription = subscription
@@ -187,6 +189,48 @@ func (m UI) View() string {
 	return m.frame.View()
 }
 
+var (
+	logTitleStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("8")) // dark grey
+	// the first log line gets a branch pointing at it from the title, the rest are indented to match
+	logBranch = logTitleStyle.Render("└─▶") + " "
+	logIndent = "    "
+)
+
+// logFooter decorates log entries drawn below the TUI with a one-time title (written when the first entry arrives)
+// and a branch from the title to the first log line. Writes are serialized by the logger.
+type logFooter struct {
+	w       io.Writer
+	started bool
+}
+
+func (l *logFooter) Write(p []byte) (int, error) {
+	var buf bytes.Buffer
+	first := !l.started
+	if first {
+		buf.WriteString(logTitleStyle.Render("Logs (non-fatal, see -v for more):") + "\n")
+		l.started = true
+	}
+	for i, line := range bytes.SplitAfter(p, []byte("\n")) {
+		if len(line) == 0 {
+			continue
+		}
+		if first && i == 0 {
+			buf.WriteString(logBranch)
+		} else {
+			buf.WriteString(logIndent)
+		}
+		buf.Write(line)
+	}
+	if _, err := l.w.Write(buf.Bytes()); err != nil {
+		return 0, err
+	}
+	return len(p), nil
+}
+
+// IsTerminal marks the footer as terminal-bound (it is drawn by the TUI) so the logger keeps colors. NO_COLOR is
+// still honored by the formatter.
+func (*logFooter) IsTerminal() bool { return true }
+
 func runWithTimeout(timeout time.Duration, fn func() error) (err error) {
 	c := make(chan struct{}, 1)
 	go func() {