Make tea issues create honor --output json (#1114)

## Problem

Follow-up to #1111, covering the issues side of the same hole: `tea issues create` accepts `--output` (it parses through the urfave/cli v3 ancestor-flag cascade — `issues` carries the flag via `AllDefaultFlags`, `create` never declares it) but the action never reads it. Without this fix, `tea issues create --output json | jq .url` feeds jq a markdown document.

The default output is doubly hostile to consumers: glamour renders the details as markdown (with OSC 8 hyperlinks around the URL when piped), and a second bare `fmt.Println(issue.HTMLURL)` line follows it.

## What this changes

- `task.CreateIssue` now returns the created `*gitea.Issue` instead of printing it.
- `runIssuesCreate` switches on `--output`, mirroring the detail-command precedent and the merged create-PR behavior from #1111: `--output json` emits compact lean JSON; any other value (or no flag) falls through to the previous rendering, byte-identical to before.
- Lean JSON shape: `index`, `title`, `url`, `state` — matching `createdPullJSON` in `cmd/pulls/create.go`, including its post-review compact encoding.
- The interactive path is untouched — it only triggers when zero flags are set, so `--output` can never be active there.

Example:

```
$ tea issues create --output json --title "bug: thing" | jq -r .url
https://gitea.example.com/owner/repo/issues/42
```

There is no agit-flow equivalent on issues, so no extra guard is needed — unlike the pulls side, every creation path produces an `*gitea.Issue`.

---------

Co-authored-by: Danilo Sousa <code@danilosousa.net>
Reviewed-on: https://gitea.com/gitea/tea/pulls/1114
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: ongolk <238961+ongolk@noreply.gitea.com>

cmd/issues/create_test.go

@@ -0,0 +1,41 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package issues
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+
+	gitea "gitea.dev/sdk"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestWriteCreatedIssueAsJSON(t *testing.T) {
+	issue := &gitea.Issue{
+		Index:   42,
+		Title:   "test title",
+		HTMLURL: "https://gitea.example.com/owner/repo/issues/42",
+		State:   gitea.StateOpen,
+	}
+
+	var buf bytes.Buffer
+	require.NoError(t, writeCreatedIssueAsJSON(&buf, issue))
+
+	var got map[string]any
+	require.NoError(t, json.Unmarshal(buf.Bytes(), &got))
+
+	assert.Equal(t, float64(42), got["index"])
+	assert.Equal(t, "test title", got["title"])
+	assert.Equal(t, "https://gitea.example.com/owner/repo/issues/42", got["url"])
+	assert.Equal(t, "open", got["state"])
+
+	// exactly the lean field set, nothing extra
+	assert.Len(t, got, 4)
+
+	// machine-readable output must not contain terminal escape sequences
+	assert.NotContains(t, buf.String(), "\x1b")
+}