feat(comments): accept -d/--description for comment body (#1043)

Closes #1042.

### What

`tea issue create`, `tea issue edit` and `tea pr create` all take the body via
`-d` / `--description`, but `tea comments add` and `tea comments edit` only
accepted it positionally — passing `-d` errored with
`flag provided but not defined: -d`.

This adds `-d` / `--description` to both `comments` subcommands so every
body-bearing command shares one flag.

### Behaviour / precedence

Unchanged for existing usage. Body resolution is now:

1. positional argument (kept first for back-compat),
2. `-d` / `--description`,
3. piped stdin,
4. `$EDITOR` (interactive only).

### Testing

- `go build`, `go vet ./...`, `go test -short ./cmd/... ./modules/...` all pass.
- Manually verified `tea comments add --help` / `edit --help` list the flag,
  and that `-d` resolves the body (reaches the API, no parse error, no editor
  prompt, no stdin block).

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/1043
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Brien Coffield <coffbr01@gmail.com>
Co-committed-by: Brien Coffield <coffbr01@gmail.com>

cmd/comments/add.go

@@ -7,7 +7,6 @@ import (
 	stdctx "context"
 	"errors"
 	"fmt"
-	"io"
 	"strings"
 
 	gitea "gitea.dev/sdk"
@@ -32,7 +31,13 @@ var CmdCommentsAdd = cli.Command{
 	Description: "Add a comment to an issue or pull request.",
 	ArgsUsage:   "<issue / pr index> [<comment body>]",
 	Action:      RunCommentsAdd,
-	Flags:       flags.AllDefaultFlags,
+	Flags: append([]cli.Flag{
+		&cli.StringFlag{
+			Name:    "description",
+			Aliases: []string{"d"},
+			Usage:   "comment body (alternative to the positional argument)",
+		},
+	}, flags.AllDefaultFlags...),
 }
 
 // RunCommentsAdd creates a new comment.
@@ -54,18 +59,12 @@ func RunCommentsAdd(requestCtx stdctx.Context, cmd *cli.Command) error {
 		return err
 	}
 
-	body := strings.Join(ctx.Args().Tail(), " ")
-	// Only consume stdin if no positional body was given. interact.IsStdinPiped()
-	// is true for any non-TTY stdin (CI, subshells, agent harnesses) — not just
-	// piped data — so reading unconditionally would block forever in those
-	// contexts when the body is supplied via args.
-	if len(body) == 0 && interact.IsStdinPiped() {
-		if bodyStdin, err := io.ReadAll(ctx.Reader); err != nil {
-			return err
-		} else if len(bodyStdin) != 0 {
-			body = string(bodyStdin)
-		}
-	} else if len(body) == 0 {
+	stdinPiped := interact.IsStdinPiped()
+	body, err := resolveBody(strings.Join(ctx.Args().Tail(), " "), ctx.String("description"), stdinPiped, ctx.Reader)
+	if err != nil {
+		return err
+	}
+	if len(body) == 0 && !stdinPiped {
 		if err := huh.NewForm(
 			huh.NewGroup(
 				huh.NewText().