Inline issue/comment attachments in body (#183)

The Gitea API returns an `assets` array on issue and comment responses, but the SDK structs drop it — so attachments are invisible to MCP agents.

Append each attachment as a `[name](url)` markdown link at the end of the body, mirroring how GitHub embeds attachments inline (which `github-mcp-server` preserves as-is).

**Coverage:**
- `issue_read get` — issue body attachments
- `issue_read get_comments` — issue and PR conversation comment attachments (same endpoint)
- `pull_request_read get` — PR description attachments (Gitea's `/pulls/` endpoint omits `assets`, so a follow-up best-effort call to `/issues/{n}/assets` surfaces them; PRs are issues internally)

PR review summaries and line-comment reviews don't support attachments per the Gitea API spec, so nothing to do there.

Closes https://gitea.com/gitea/gitea-mcp/issues/182

---
This PR was written with the help of Claude Opus 4.7

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/183
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

operation/issue/slim_test.go

@@ -40,6 +40,29 @@ func TestSlimIssue(t *testing.T) {
 	}
 }
 
+func TestBodyWithAttachments(t *testing.T) {
+	atts := []*gitea_sdk.Attachment{
+		{Name: "shot.png", DownloadURL: "https://example/shot.png"},
+		{Name: "log.txt", DownloadURL: "https://example/log.txt"},
+	}
+	got := bodyWithAttachments("see attached", atts)
+	want := "see attached\n\n[shot.png](https://example/shot.png)\n[log.txt](https://example/log.txt)"
+	if got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+
+	if got := bodyWithAttachments("only body", nil); got != "only body" {
+		t.Errorf("nil attachments should return body unchanged, got %q", got)
+	}
+	if got := bodyWithAttachments("", atts); got != "[shot.png](https://example/shot.png)\n[log.txt](https://example/log.txt)" {
+		t.Errorf("empty body should drop separator, got %q", got)
+	}
+	skipped := []*gitea_sdk.Attachment{nil, {Name: "noop", DownloadURL: ""}}
+	if got := bodyWithAttachments("body", skipped); got != "body" {
+		t.Errorf("nil/empty-URL attachments should be skipped, got %q", got)
+	}
+}
+
 func TestSlimIssues_ListIsSlimmer(t *testing.T) {
 	i := &gitea_sdk.Issue{
 		Index:  1,