Refactor pip install (flagos-ai#1109)

### PR Category
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Hardware | CICD | Tools | Others ] -->
Tools

### PR Types
<!-- One of [ User Experience | New Features | Bug Fixes | Improvements
| Performance | Breaking Change| Deprecations | Test Case | Docs |
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Improvements

### PR Description
<!-- Describe what you’ve done -->
Refactor the installation process for FlagScale to make it easier for
users to install with pip.
`FLAGSCALE_PLATFORM=cuda FLAGSCALE_TASK=train pip install
--no-build-isolation . -vvv`

Author: aoyulong

.coveragerc

@@ -162,6 +162,7 @@ jobs:
             ${INSTALL_DIR:+--install-dir "$INSTALL_DIR"} \
             --no-system --no-dev --no-base --no-task \
             --src-deps megatron-lm \
+            --pip-deps typer \
             --retry-count 3
 
           # Copy test data (keep existing logic)

.github/workflows/unit_tests_common.yml

@@ -1,11 +0,0 @@
-import os
-import sys
-
-# Add parent directory to path to import version
-_parent_dir = os.path.dirname(os.path.abspath(__file__))
-if _parent_dir not in sys.path:
-    sys.path.insert(0, _parent_dir)
-
-from version import FLAGSCALE_VERSION
-
-__version__ = FLAGSCALE_VERSION

__init__.py

@@ -0,0 +1,27 @@
+def _get_version() -> str:
+    """Get version from importlib.metadata or parse pyproject.toml as fallback."""
+    try:
+        from importlib.metadata import version
+
+        return version("flagscale")
+    except Exception:
+        pass
+
+    # Fallback: parse pyproject.toml for development mode (Python 3.11+)
+    try:
+        from pathlib import Path
+
+        import tomllib
+
+        pyproject_path = Path(__file__).parent.parent / "pyproject.toml"
+        if pyproject_path.exists():
+            with open(pyproject_path, "rb") as f:
+                data = tomllib.load(f)
+                return data.get("project", {}).get("version", "0.0.0")
+    except Exception:
+        pass
+
+    return "0.0.0"
+
+
+__version__ = _get_version()