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/pager.go

@@ -0,0 +1,69 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package terminal
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// Pager renders multi-line human output through an external command.
+type Pager interface {
+	Page(context.Context, string, io.Reader, Streams) error
+}
+
+// SystemPager runs the pager without a shell and routes diagnostics to stderr.
+type SystemPager struct{}
+
+// Page validates the command and feeds content to the pager stdin. The pager
+// handles interrupts itself; killing it on cancellation would leave the terminal raw.
+func (SystemPager) Page(ctx context.Context, command string, input io.Reader, streams Streams) error {
+	args, ok := commandArgs(command)
+	if !ok {
+		return errors.New("pager command contains malformed quoted arguments")
+	}
+	process := exec.Command(args[0], args[1:]...)
+	process.Stdin = input
+	process.Stdout = streams.Out
+	process.Stderr = streams.ErrOut
+	env := os.Environ()
+	if os.Getenv("LESS") == "" {
+		env = append(env, "LESS=FRX")
+	}
+	process.Env = env
+	if err := process.Run(); err != nil {
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
+		return fmt.Errorf("pager failed; configure pager or PAGER: %w", err)
+	}
+	return nil
+}
+
+// WriteHuman writes human text directly, or through a pager when stdout is a TTY,
+// a pager command is configured, and the content spans multiple lines.
+// Prompting policy such as --no-input does not affect paging.
+func WriteHuman(ctx context.Context, streams Streams, command string, pager Pager, text string) error {
+	if !shouldPage(streams, command, text) {
+		_, err := io.WriteString(streams.Out, text)
+		return err
+	}
+	if pager == nil {
+		pager = SystemPager{}
+	}
+	return pager.Page(ctx, command, strings.NewReader(text), streams)
+}
+
+func shouldPage(streams Streams, command, text string) bool {
+	if !streams.OutTTY || command == "" || command == "cat" {
+		return false
+	}
+	trimmed := strings.TrimSuffix(text, "\n")
+	return strings.Contains(trimmed, "\n")
+}