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/browser_test.go

@@ -0,0 +1,37 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package terminal
+
+import (
+	"bytes"
+	"context"
+	"os/exec"
+	"testing"
+
+	"github.com/kballard/go-shellquote"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBrowserRejectsInvalidURLsBeforeLaunchingCommand(t *testing.T) {
+	for _, resource := range []string{"javascript:alert(1)", "file:///tmp/file", "https://user:secret@example.org", "https://example.org\n"} {
+		err := (SystemBrowser{}).Open(context.Background(), resource, "missing-browser-command")
+		require.ErrorContains(t, err, "resource URL without credentials")
+		require.NotContains(t, err.Error(), "secret")
+	}
+}
+
+func TestBrowserUsesLiteralArgumentsAndDiagnosticWriter(t *testing.T) {
+	printf, err := exec.LookPath("printf")
+	if err != nil {
+		t.Skip("printf executable is unavailable")
+	}
+	var diagnostics bytes.Buffer
+	resource := "https://example.org/$(echo-secret)"
+	command := shellquote.Join(printf, "%s")
+	require.NoError(t, (SystemBrowser{ErrOut: &diagnostics}).Open(context.Background(), resource, command))
+	require.Equal(t, resource, diagnostics.String())
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	require.ErrorIs(t, (SystemBrowser{}).Open(ctx, resource, command), context.Canceled)
+}