feat: implement markitect installer with version/release commands (issue #80)

- Add comprehensive version information system with git integration
- Add `markitect version` and `markitect release` commands with multiple output formats
- Add global `--version` flag for quick version checking
- Create Python installer script with advanced options (install.py)
- Create shell installer wrapper for easy installation (install.sh)
- Add comprehensive installation documentation (INSTALL.md)
- Support user and system-wide installations with virtual environments
- Include development mode installation with test dependencies
- Add installation status checking and uninstall functionality

Commands added:
- `markitect --version` - Quick version display
- `markitect version [--short]` - Detailed version information
- `markitect release [--format text|json|yaml]` - Release information

Installer features:
- Automatic virtual environment creation
- Symbolic link management for global access
- Custom installation paths and prefixes
- Development mode with test dependencies
- Installation validation and troubleshooting

Resolves #80

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

markitect/__version__.py

@@ -0,0 +1,123 @@
+"""
+Version information for MarkiTect.
+
+This module provides version and release information for the MarkiTect package.
+Version information is sourced from pyproject.toml and git metadata when available.
+"""
+
+import os
+import subprocess
+from pathlib import Path
+from typing import Optional
+
+# Base version from pyproject.toml
+__version__ = "0.1.0"
+
+def get_git_commit_hash() -> Optional[str]:
+    """Get the current git commit hash if available."""
+    try:
+        result = subprocess.run(
+            ['git', 'rev-parse', '--short', 'HEAD'],
+            capture_output=True,
+            text=True,
+            check=True,
+            cwd=Path(__file__).parent.parent
+        )
+        return result.stdout.strip()
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        return None
+
+def get_git_branch() -> Optional[str]:
+    """Get the current git branch if available."""
+    try:
+        result = subprocess.run(
+            ['git', 'branch', '--show-current'],
+            capture_output=True,
+            text=True,
+            check=True,
+            cwd=Path(__file__).parent.parent
+        )
+        return result.stdout.strip()
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        return None
+
+def get_git_tag() -> Optional[str]:
+    """Get the current git tag if available."""
+    try:
+        result = subprocess.run(
+            ['git', 'describe', '--tags', '--exact-match'],
+            capture_output=True,
+            text=True,
+            check=True,
+            cwd=Path(__file__).parent.parent
+        )
+        return result.stdout.strip()
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        return None
+
+def is_development_version() -> bool:
+    """Check if this is a development version (has uncommitted changes)."""
+    try:
+        result = subprocess.run(
+            ['git', 'status', '--porcelain'],
+            capture_output=True,
+            text=True,
+            check=True,
+            cwd=Path(__file__).parent.parent
+        )
+        return bool(result.stdout.strip())
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        return False
+
+def get_version_info() -> dict:
+    """Get comprehensive version information."""
+    git_commit = get_git_commit_hash()
+    git_branch = get_git_branch()
+    git_tag = get_git_tag()
+    is_dev = is_development_version()
+
+    # Build version string
+    version_parts = [__version__]
+
+    if git_tag and git_tag != f"v{__version__}":
+        # If we have a different tag, use it
+        version_parts = [git_tag.lstrip('v')]
+
+    if git_commit:
+        if is_dev:
+            version_parts.append(f"dev+{git_commit}")
+        elif not git_tag:
+            version_parts.append(f"+{git_commit}")
+
+    if is_dev and not git_commit:
+        version_parts.append("dev")
+
+    full_version = ".".join(version_parts)
+
+    return {
+        "version": __version__,
+        "full_version": full_version,
+        "git_commit": git_commit,
+        "git_branch": git_branch,
+        "git_tag": git_tag,
+        "is_development": is_dev,
+        "is_git_repo": git_commit is not None
+    }
+
+def get_release_info() -> dict:
+    """Get release information."""
+    version_info = get_version_info()
+
+    release_type = "development" if version_info["is_development"] else "release"
+    if version_info["git_tag"]:
+        release_type = "tagged-release"
+    elif version_info["git_commit"] and not version_info["is_development"]:
+        release_type = "commit-build"
+
+    return {
+        "release_type": release_type,
+        "build_from": version_info["git_branch"] or "unknown",
+        "commit": version_info["git_commit"] or "unknown",
+        "clean_build": not version_info["is_development"],
+        **version_info
+    }