refactor: add terminal output and forms package (#1124)

- `internal/terminal`: streams and the prompting policy, interactive forms (issue, PR, review, merge, milestone), editor / pager / browser launching, JSON and `--jq` output.
- An aligned table renderer and a record renderer for human output; both strip control and escape characters from server-supplied text so titles and bodies cannot inject terminal sequences.

Reviewed-on: https://gitea.com/gitea/tea/pulls/1124
Reviewed-by: TheFox0x7 <95654+thefox0x7@noreply.gitea.com>

internal/terminal/milestone_form_test.go

@@ -0,0 +1,18 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package terminal
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestMilestoneFormMarksTitleRequired(t *testing.T) {
+	p, rendered := accessiblePrompter(t, "v1\n\n\n")
+	_, err := p.CreateMilestone(context.Background())
+	require.NoError(t, err)
+	require.Contains(t, rendered.String(), "Milestone title (required):")
+}