feat(update): add full update command with add-style specs and CLI integration

- introduce UpdateCommand with support for:
  • full update (all dependencies)
  • targeted update (one or more packages)
  • add-style specs (@namespace/name[@Version])
  • options: --dry-run, --json, --install

- reuse AddCommand for version resolution and installation
- validate targets against vix.lock before updating
- integrate command into Dispatcher and CLI help
- update CLI help output for better discoverability

Enables 'vix update' as a first-class dependency management command.

Author: GaspardKirira

include/vix/cli/commands/UpdateCommand.hpp

@@ -0,0 +1,29 @@
+/**
+ *
+ *  @file UpdateCommand.hpp
+ *  @author Gaspard Kirira
+ *
+ *  Copyright 2025, Gaspard Kirira.  All rights reserved.
+ *  https://github.com/vixcpp/vix
+ *  Use of this source code is governed by a MIT license
+ *  that can be found in the License file.
+ *
+ *  Vix.cpp
+ *
+ */
+#ifndef VIX_UPDATE_COMMAND_HPP
+#define VIX_UPDATE_COMMAND_HPP
+
+#include <string>
+#include <vector>
+
+namespace vix::commands
+{
+  struct UpdateCommand
+  {
+    static int run(const std::vector<std::string> &args);
+    static int help();
+  };
+}
+
+#endif

src/CLI.cpp

@@ -39,6 +39,7 @@
 #include <vix/cli/commands/DoctorCommand.hpp>
 #include <vix/cli/commands/UninstallCommand.hpp>
 #include <vix/cli/commands/UnpublishCommand.hpp>
+#include <vix/cli/commands/UpdateCommand.hpp>
 #include <vix/utils/Env.hpp>
 #include <vix/cli/Style.hpp>
 #include <vix/utils/Logger.hpp>
@@ -353,6 +354,8 @@ namespace vix
         return commands::RegistryCommand::help();
       if (cmd == "add")
         return commands::AddCommand::help();
+      if (cmd == "update")
+        return commands::UpdateCommand::help();
       if (cmd == "search")
         return commands::SearchCommand::help();
       if (cmd == "remove")
@@ -436,6 +439,7 @@ namespace vix
     docs("https://vixcpp.com/docs/modules/cli/search");
     out << indent(3) << "add <pkg>@<ver>   Add dependency\n";
     out << indent(3) << "install           Install dependencies\n";
+    out << indent(3) << "update            Update dependencies\n";
     out << indent(3) << "i                 Alias for install\n";
     out << indent(3) << "deps              Legacy alias for install\n";
     out << indent(3) << "remove <pkg>      Remove dependency\n";

src/commands/Dispatch.cpp

@@ -37,6 +37,7 @@
 #include <vix/cli/commands/DoctorCommand.hpp>
 #include <vix/cli/commands/UninstallCommand.hpp>
 #include <vix/cli/commands/UnpublishCommand.hpp>
+#include <vix/cli/commands/UpdateCommand.hpp>
 #include <vix/cli/util/Ui.hpp>
 
 #include <stdexcept>
@@ -196,6 +197,22 @@ namespace vix::cli::dispatch
          []()
          { return vix::commands::ListCommand::help(); }});
 
+    add({"update",
+         "Registry",
+         "Update all dependencies to latest versions",
+         [](const Args &a)
+         { return vix::commands::UpdateCommand::run(a); },
+         []()
+         { return vix::commands::UpdateCommand::help(); }});
+
+    add({"up",
+         "Registry",
+         "Alias for update",
+         [](const Args &a)
+         { return vix::commands::UpdateCommand::run(a); },
+         []()
+         { return vix::commands::UpdateCommand::help(); }});
+
     add({"store",
          "Registry",
          "Manage local store cache (gc/path)",