Add tool annotations and PR close/reopen support (#174)

Add MCP `ToolAnnotation` metadata (Title, ReadOnlyHint, DestructiveHint)
to all registered tools so MCP hosts (VS Code, Claude, Cursor) get
accurate per-tool hints. A shared `pkg/annotation` package exposes
`ReadOnly`, `Write`, and `Destructive` helpers for consistency.

Add `close` and `reopen` methods to `pull_request_write` so PR state
can be toggled without going through the generic `update` path.

Co-Authored-By: silverwind <me@silverwind.io>
Co-Authored-By: Claude (Opus 4.7) <noreply@anthropic.com>

operation/repo/branch.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 
+	"gitea.com/gitea/gitea-mcp/pkg/annotation"
 	"gitea.com/gitea/gitea-mcp/pkg/gitea"
 	"gitea.com/gitea/gitea-mcp/pkg/log"
 	"gitea.com/gitea/gitea-mcp/pkg/params"
@@ -24,6 +25,7 @@ var (
 	CreateBranchTool = mcp.NewTool(
 		CreateBranchToolName,
 		mcp.WithDescription("Create branch"),
+		mcp.WithToolAnnotation(annotation.Write("Create a new branch")),
 		mcp.WithString("owner", mcp.Required(), mcp.Description("repository owner")),
 		mcp.WithString("repo", mcp.Required(), mcp.Description("repository name")),
 		mcp.WithString("branch", mcp.Required(), mcp.Description("Name of the branch to create")),
@@ -33,6 +35,7 @@ var (
 	DeleteBranchTool = mcp.NewTool(
 		DeleteBranchToolName,
 		mcp.WithDescription("Delete branch"),
+		mcp.WithToolAnnotation(annotation.Destructive("Delete a branch")),
 		mcp.WithString("owner", mcp.Required(), mcp.Description("repository owner")),
 		mcp.WithString("repo", mcp.Required(), mcp.Description("repository name")),
 		mcp.WithString("branch", mcp.Required(), mcp.Description("Name of the branch to delete")),
@@ -41,6 +44,7 @@ var (
 	ListBranchesTool = mcp.NewTool(
 		ListBranchesToolName,
 		mcp.WithDescription("List branches"),
+		mcp.WithToolAnnotation(annotation.ReadOnly("List repository branches")),
 		mcp.WithString("owner", mcp.Required(), mcp.Description("repository owner")),
 		mcp.WithString("repo", mcp.Required(), mcp.Description("repository name")),
 		mcp.WithNumber("page", mcp.Description("page number"), mcp.DefaultNumber(1)),