fix(tui): wrap long artifact lines in viewer instead of truncating

Artifact content wider than the modal was silently cut off. Lines are now
hard-wrapped at rune boundaries to the modal content width, and scroll
clamping uses the wrapped line count so the last page stays reachable.

apps/tui-go/internal/app/overlays.go

@@ -440,8 +440,9 @@ func (m Model) artifactContentBodyH() int {
 	return h
 }
 
-// artifactContentLines splits the selected artifact's content into display lines.
-func (m Model) artifactContentLines() []string {
+// artifactContentLines splits the selected artifact's content into display lines,
+// wrapping each line to the specified width.
+func (m Model) artifactContentLines(w int) []string {
 	if m.artifactsIndex < 0 || m.artifactsIndex >= len(m.artifacts) {
 		return nil
 	}
@@ -449,12 +450,13 @@ func (m Model) artifactContentLines() []string {
 	if c == nil {
 		return []string{"(no content stored)"}
 	}
-	return strings.Split(strings.ReplaceAll(*c, "\r\n", "\n"), "\n")
+	lines := strings.Split(strings.ReplaceAll(*c, "\r\n", "\n"), "\n")
+	return wrapLines(lines, w)
 }
 
 // artifactContentMaxScroll keeps the last page of content anchored to the body bottom.
-func (m Model) artifactContentMaxScroll() int {
-	max := len(m.artifactContentLines()) - m.artifactContentBodyH()
+func (m Model) artifactContentMaxScroll(w int) int {
+	max := len(m.artifactContentLines(w)) - m.artifactContentBodyH()
 	if max < 0 {
 		max = 0
 	}
@@ -515,11 +517,13 @@ func (m Model) artifactsModal() string {
 	}
 
 	// Selected artifact content, scrollable with PgUp/PgDn.
-	lines := m.artifactContentLines()
+	// Width available for content: w - 2 (left padding) - 2 (box borders) - 2 (right padding) = w - 6
+	contentW := w - 6
+	lines := m.artifactContentLines(contentW)
 	bodyH := m.artifactContentBodyH()
 	coff := m.artifactScroll
-	if coff > m.artifactContentMaxScroll() {
-		coff = m.artifactContentMaxScroll()
+	if coff > m.artifactContentMaxScroll(contentW) {
+		coff = m.artifactContentMaxScroll(contentW)
 	}
 	if coff < 0 {
 		coff = 0
@@ -534,7 +538,7 @@ func (m Model) artifactsModal() string {
 		cend = len(lines)
 	}
 	for i := coff; i < cend; i++ {
-		b.WriteString(mbg(t, "  "+truncate(lines[i], w-6), t.P.Fg) + "\n")
+		b.WriteString(mbg(t, "  "+lines[i], t.P.Fg) + "\n")
 	}
 
 	b.WriteString("\n" + modalHints(t, [][2]string{{"↑↓", "select"}, {"PgUp/Dn", "scroll"}, {"v/esc", "close"}}))
@@ -582,3 +586,37 @@ func truncate(s string, w int) string {
 	}
 	return string(r[:w-1]) + "…"
 }
+
+// wrapLines wraps each line in the input slice to the specified width using hard rune-boundary wrapping.
+func wrapLines(lines []string, w int) []string {
+	if w < 1 {
+		w = 1
+	}
+	var result []string
+	for _, line := range lines {
+		wrapped := wrapLine(line, w)
+		result = append(result, wrapped...)
+	}
+	return result
+}
+
+// wrapLine wraps a single line to the specified width using hard rune-boundary wrapping.
+func wrapLine(s string, w int) []string {
+	if w < 1 {
+		w = 1
+	}
+	runes := []rune(s)
+	if len(runes) <= w {
+		return []string{s}
+	}
+	var lines []string
+	for len(runes) > 0 {
+		if len(runes) <= w {
+			lines = append(lines, string(runes))
+			break
+		}
+		lines = append(lines, string(runes[:w]))
+		runes = runes[w:]
+	}
+	return lines
+}