fix(msgfmt): teach message box detection about the elusive U+254C dashed line

Claude Code v2.1.87 decided to get fancy with its onboarding screen,
using ╌ (BOX DRAWINGS LIGHT DOUBLE DASH HORIZONTAL) instead of the
classic ─ (BOX DRAWINGS LIGHT HORIZONTAL). Our detector stared at
this new character like a cat seeing a cucumber.

Add ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ as an alternative pattern in both
findGreaterThanMessageBox and findGenericSlimMessageBox.

Refs: #209

Author: johnstcn

lib/msgfmt/message_box.go

@@ -12,7 +12,7 @@ import (
 func findGreaterThanMessageBox(lines []string) int {
 	for i := len(lines) - 1; i >= max(len(lines)-6, 0); i-- {
 		if strings.Contains(lines[i], ">") {
-			if i > 0 && strings.Contains(lines[i-1], "───────────────") {
+			if i > 0 && (strings.Contains(lines[i-1], "───────────────") || strings.Contains(lines[i-1], "╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌")) {
 				return i - 1
 			}
 			return i
@@ -27,9 +27,9 @@ func findGreaterThanMessageBox(lines []string) int {
 // ───────────────
 func findGenericSlimMessageBox(lines []string) int {
 	for i := len(lines) - 3; i >= max(len(lines)-9, 0); i-- {
-		if strings.Contains(lines[i], "───────────────") &&
+		if (strings.Contains(lines[i], "───────────────") || strings.Contains(lines[i], "╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌")) &&
 			(strings.Contains(lines[i+1], "|") || strings.Contains(lines[i+1], "│") || strings.Contains(lines[i+1], "❯")) &&
-			strings.Contains(lines[i+2], "───────────────") {
+			(strings.Contains(lines[i+2], "───────────────") || strings.Contains(lines[i+2], "╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌")) {
 			return i
 		}
 	}

lib/msgfmt/testdata/initialization/claude/ready/msg_dashed_box.txt

@@ -0,0 +1,8 @@
+  1  function greet() {                                                         
+  2 -  console.log("Hello, World!");                                            
+  2 +  console.log("Hello, Claude!");                                           
+  3  }                                                                          
+ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ 
+ > Try "what does this code do?"                                                
+ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ 
+  Syntax theme: Monokai Extended (ctrl+t to disable)