feat: convert attachments to text on delete (#1863)

Co-authored-by: Dax Raad <d@ironbay.co>
Co-authored-by: Dax <mail@thdxr.com>

packages/tui/internal/components/textarea/textarea_test.go

@@ -0,0 +1,75 @@
+package textarea
+
+import (
+	"testing"
+
+	"github.com/sst/opencode/internal/attachment"
+)
+
+func TestRemoveAttachmentAtCursor_ConvertsToText_WhenCursorAfterAttachment(t *testing.T) {
+	m := New()
+	m.InsertString("a ")
+	att := &attachment.Attachment{ID: "1", Display: "@file.txt"}
+	m.InsertAttachment(att)
+	m.InsertString(" b")
+
+	// Position cursor immediately after the attachment (index 3: 'a',' ',att,' ', 'b')
+	m.SetCursorColumn(3)
+
+	if ok := m.removeAttachmentAtCursor(); !ok {
+		t.Fatalf("expected removal to occur")
+	}
+	got := m.Value()
+	want := "a @file.txt b"
+	if got != want {
+		t.Fatalf("expected %q, got %q", want, got)
+	}
+}
+
+func TestRemoveAttachmentAtCursor_ConvertsToText_WhenCursorOnAttachment(t *testing.T) {
+	m := New()
+	m.InsertString("x ")
+	att := &attachment.Attachment{ID: "2", Display: "@img.png"}
+	m.InsertAttachment(att)
+	m.InsertString(" y")
+
+	// Position cursor on the attachment token (index 2: 'x',' ',att,' ', 'y')
+	m.SetCursorColumn(2)
+
+	if ok := m.removeAttachmentAtCursor(); !ok {
+		t.Fatalf("expected removal to occur")
+	}
+	got := m.Value()
+	want := "x @img.png y"
+	if got != want {
+		t.Fatalf("expected %q, got %q", want, got)
+	}
+}
+
+func TestRemoveAttachmentAtCursor_StartOfLine(t *testing.T) {
+	m := New()
+	att := &attachment.Attachment{ID: "3", Display: "@a.txt"}
+	m.InsertAttachment(att)
+	m.InsertString(" tail")
+
+	// Position cursor immediately after the attachment at start of line (index 1)
+	m.SetCursorColumn(1)
+	if ok := m.removeAttachmentAtCursor(); !ok {
+		t.Fatalf("expected removal to occur at start of line")
+	}
+	if got := m.Value(); got != "@a.txt tail" {
+		t.Fatalf("unexpected value: %q", got)
+	}
+}
+
+func TestRemoveAttachmentAtCursor_NoAttachment_NoChange(t *testing.T) {
+	m := New()
+	m.InsertString("hello world")
+	col := m.CursorColumn()
+	if ok := m.removeAttachmentAtCursor(); ok {
+		t.Fatalf("did not expect removal to occur")
+	}
+	if m.Value() != "hello world" || m.CursorColumn() != col {
+		t.Fatalf("value or cursor unexpectedly changed")
+	}
+}