Add package listing and management tools (#170)

Adds `package_read` and `package_write` MCP tools for the Gitea
Packages API.

- `package_read` (read): `list`, `list_versions`, `get`
- `package_write` (write): `delete`

Package names containing slashes (e.g. container image paths like
`my-repo/my-image`) are accepted raw or pre-encoded and URL-encoded
correctly without double-encoding.

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

operation/packages/slim.go

@@ -0,0 +1,43 @@
+package packages
+
+func slimPackage(v any) map[string]any {
+	m, ok := v.(map[string]any)
+	if !ok {
+		return nil
+	}
+	out := map[string]any{
+		"id":         m["id"],
+		"type":       m["type"],
+		"name":       m["name"],
+		"version":    m["version"],
+		"html_url":   m["html_url"],
+		"created_at": m["created_at"],
+	}
+	if owner, ok := m["owner"].(map[string]any); ok {
+		out["owner"] = owner["login"]
+	}
+	if creator, ok := m["creator"].(map[string]any); ok {
+		out["creator"] = creator["login"]
+	}
+	if repo, ok := m["repository"].(map[string]any); ok {
+		out["repository"] = repo["full_name"]
+	}
+	return out
+}
+
+func slimPackages(v any) any {
+	switch val := v.(type) {
+	case []any:
+		out := make([]map[string]any, 0, len(val))
+		for _, item := range val {
+			if slim := slimPackage(item); slim != nil {
+				out = append(out, slim)
+			}
+		}
+		return out
+	case map[string]any:
+		return slimPackage(val)
+	default:
+		return v
+	}
+}