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.go

@@ -9,6 +9,8 @@
 //	agentpr issue create --repo owner/repo --title T --body B
 //	agentpr issue comment --repo owner/repo --issue 12 --body "..."
 //	agentpr issue edit --repo owner/repo --issue 12 --title T --body B
+//	agentpr issue close --repo owner/repo --issue 12
+//	agentpr issue reopen --repo owner/repo --issue 12
 //	agentpr whoami
 package main
 
@@ -69,9 +71,15 @@ func newPRCmd() *cobra.Command {
 func newIssueCmd() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "issue",
-		Short: "File and edit issues, and post issue comments",
+		Short: "File, edit, close and reopen issues, and post issue comments",
 	}
-	cmd.AddCommand(newIssueCreateCmd(), newCommentCmd("issue", "issue", "Post a comment on an issue"), newIssueEditCmd())
+	cmd.AddCommand(
+		newIssueCreateCmd(),
+		newCommentCmd("issue", "issue", "Post a comment on an issue"),
+		newIssueEditCmd(),
+		newIssueStateCmd("close", "Close an issue", agent.IssueStateClosed),
+		newIssueStateCmd("reopen", "Reopen a closed issue", agent.IssueStateOpen),
+	)
 	return cmd
 }
 
@@ -301,6 +309,44 @@ func newIssueEditCmd() *cobra.Command {
 	return cmd
 }
 
+// newIssueStateCmd builds `issue close` and `issue reopen`, which differ only
+// in the state they ask for. An issue already in that state is an error, not a
+// silent success: Gitea answers the PATCH with 200 either way.
+func newIssueStateCmd(use, short, state string) *cobra.Command {
+	var repo string
+	var issue int
+	cmd := &cobra.Command{
+		Use:          use,
+		Short:        short,
+		SilenceUsage: true,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			owner, name, err := agent.ParseRepo(repo)
+			if err != nil {
+				return err
+			}
+			if issue <= 0 {
+				return fmt.Errorf("--issue must be a positive issue number")
+			}
+			c, err := client()
+			if err != nil {
+				return err
+			}
+			updated, err := c.SetIssueState(owner+"/"+name, issue, state)
+			if err != nil {
+				return err
+			}
+			fmt.Printf("#%d %s %s\n", updated.Number, updated.State, updated.HTMLURL)
+			return nil
+		},
+	}
+	f := cmd.Flags()
+	f.StringVar(&repo, "repo", "", "Repository as owner/repo (required)")
+	f.IntVar(&issue, "issue", 0, "Issue number (required)")
+	_ = cmd.MarkFlagRequired("repo")
+	_ = cmd.MarkFlagRequired("issue")
+	return cmd
+}
+
 func newWhoamiCmd() *cobra.Command {
 	return &cobra.Command{
 		Use:          "whoami",