agentpr: close and reopen issues

- add issue close and issue reopen subcommands
- add GetIssue and SetIssueState to the Gitea client
- fail when the issue is already in the requested state
- document the new subcommands in README.md and AGENTS.md

cmd/agentpr/main_test.go

@@ -149,3 +149,56 @@ func TestCommentCommandsStayInStep(t *testing.T) {
 		t.Error("issue comment must take --issue and only --issue")
 	}
 }
+
+// Both state commands need a repo and an issue number; cobra and the RunE
+// guard must reject their absence before anything reaches for a token.
+func TestIssueStateCommandsRequireFlags(t *testing.T) {
+	for _, verb := range []string{"close", "reopen"} {
+		t.Run(verb+" without --issue", func(t *testing.T) {
+			err := execute("issue", verb, "--repo", "unkin/repo")
+			if err == nil {
+				t.Fatal("Execute() = nil, want an error when --issue is missing")
+			}
+			if !strings.Contains(err.Error(), "issue") {
+				t.Errorf("error = %q, want it to name the missing --issue flag", err)
+			}
+		})
+		t.Run(verb+" without --repo", func(t *testing.T) {
+			err := execute("issue", verb, "--issue", "12")
+			if err == nil {
+				t.Fatal("Execute() = nil, want an error when --repo is missing")
+			}
+			if !strings.Contains(err.Error(), "repo") {
+				t.Errorf("error = %q, want it to name the missing --repo flag", err)
+			}
+		})
+		t.Run(verb+" with a zero --issue", func(t *testing.T) {
+			err := execute("issue", verb, "--repo", "unkin/repo", "--issue", "0")
+			if err == nil {
+				t.Fatal("Execute() = nil, want an error for a non-positive issue number")
+			}
+			if !strings.Contains(err.Error(), "--issue must be a positive") {
+				t.Errorf("error = %q, want it to reject the issue number", err)
+			}
+		})
+		t.Run(verb+" with a malformed --repo", func(t *testing.T) {
+			if err := execute("issue", verb, "--repo", "not-a-repo", "--issue", "12"); err == nil {
+				t.Fatal("Execute() = nil, want error for a malformed --repo")
+			}
+		})
+	}
+}
+
+// Closing and reopening are issue-only: a PR is closed by a human, so the pr
+// group must not grow these verbs by accident.
+func TestPRHasNoStateCommands(t *testing.T) {
+	for _, verb := range []string{"close", "reopen"} {
+		if cmd, _, err := newRootCmd().Find([]string{"pr", verb}); err == nil && cmd.Name() == verb {
+			t.Errorf("pr %s exists; closing a PR is not agentpr's to do", verb)
+		}
+		cmd, _, err := newRootCmd().Find([]string{"issue", verb})
+		if err != nil || cmd.Name() != verb {
+			t.Fatalf("issue %s not found: %v", verb, err)
+		}
+	}
+}