chore: release v6.4.1

- Bump version to 6.4.1
- Update CHANGELOG.md with release notes
- Update README.md with new version
- Update version references

Release: v6.4.1

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

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

Author: marcusgoll

CHANGELOG.md

@@ -2,6 +2,22 @@
 
 ---
 
+## [6.4.1] - 2025-11-17
+
+### Fixed
+- **Windows Compatibility**: Added automatic bash fallback in spec-cli.py when PowerShell scripts don't exist
+  - Enables Windows users to run workflow commands via Git Bash/WSL
+  - Falls back gracefully with informative message when PowerShell script is missing
+  - Fixes "PowerShell script not found" error for feature-workflow and other commands
+- **Git Permissions**: Fixed executable permissions for ship-prod-workflow.sh
+
+### Technical Details
+- Modified `run_script()` in spec-cli.py to check for bash alternatives before failing
+- Added __pycache__ to .gitignore to prevent Python cache directory commits
+- All workflow scripts now properly executable in git (100755 mode)
+
+---
+
 ## [6.4.0] - 2025-11-17
 
 ### Added

README.md

@@ -44,6 +44,23 @@
 
 ## 🆕 Recent Updates
 
+### v6.4.1 (November 2025)
+
+**Windows Compatibility Fix**
+
+- **Bash Fallback**: spec-cli.py now automatically falls back to bash scripts when PowerShell equivalents don't exist
+  - Enables Windows users to run workflow commands via Git Bash/WSL without errors
+  - Graceful fallback with informative message: "Note: PowerShell script not found, using bash"
+  - Fixes "PowerShell script not found" error for feature-workflow and other commands
+- **Git Permissions**: Fixed executable permissions for ship-prod-workflow.sh (100755 mode)
+- **Python Cache**: Added __pycache__ to .gitignore to prevent accidental commits
+
+**Problem Solved**: Windows users couldn't run workflow commands because spec-cli.py expected PowerShell scripts that were never created during the CLI migration. Only bash scripts exist, but there was no fallback mechanism.
+
+**Impact**: Windows users with Git Bash/WSL can now run all workflow commands seamlessly. Cross-platform compatibility restored without requiring PowerShell script duplication.
+
+---
+
 ### v6.4.0 (November 2025)
 
 **CLI Integration & Design System Expansion**

package.json

@@ -1,6 +1,6 @@
 {
   "name": "spec-flow",
-  "version": "6.4.0",
+  "version": "6.4.1",
   "description": "Spec-Driven Development workflow toolkit for Claude Code - Build high-quality features faster with repeatable AI workflows",
   "keywords": [
     "claude",