Refactor: Restructure pkgmgr into actions/, core/, and cli/ (full module breakup)

This commit introduces a large-scale structural refactor of the pkgmgr
codebase. All functionality has been moved from the previous flat
top-level layout into three clearly separated namespaces:

  • pkgmgr.actions      – high-level operations invoked by the CLI
  • pkgmgr.core         – pure logic, helpers, repository utilities,
                          versioning, git helpers, config IO, and
                          command resolution
  • pkgmgr.cli          – parser, dispatch, context, and command
                          handlers

Key improvements:
  - Moved all “branch”, “release”, “changelog”, repo-management
    actions, installer pipelines, and proxy execution logic into
    pkgmgr.actions.<domain>.
  - Reworked installer structure under
        pkgmgr.actions.repository.install.installers
    including OS-package installers, Nix, Python, and Makefile.
  - Consolidated all low-level functionality under pkgmgr.core:
        • git helpers → core/git
        • config load/save → core/config
        • repository helpers → core/repository
        • versioning & semver → core/version
        • command helpers (alias, resolve, run, ink) → core/command
  - Replaced pkgmgr.cli_core with pkgmgr.cli and updated all imports.
  - Added minimal __init__.py files for clean package exposure.
  - Updated all E2E, integration, and unit tests with new module paths.
  - Fixed patch targets so mocks point to the new structure.
  - Ensured backward compatibility at the CLI boundary (pkgmgr entry point unchanged).

This refactor produces a cleaner, layered architecture:
  - `core` = logic
  - `actions` = orchestrated behaviour
  - `cli` = user interface

Reference: ChatGPT-assisted refactor discussion
https://chatgpt.com/share/6938221c-e24c-800f-8317-7732cedf39b9

pkgmgr/actions/repository/install/context.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+Shared context object for repository installation steps.
+
+This data class bundles all information needed by installer components so
+they do not depend on global state or long parameter lists.
+"""
+
+from dataclasses import dataclass
+from typing import Any, Dict, List
+
+
+@dataclass
+class RepoContext:
+    """Container for all repository-related data used during installation."""
+
+    repo: Dict[str, Any]
+    identifier: str
+    repo_dir: str
+    repositories_base_dir: str
+    bin_dir: str
+    all_repos: List[Dict[str, Any]]
+
+    no_verification: bool
+    preview: bool
+    quiet: bool
+    clone_mode: str
+    update_dependencies: bool