bug(windows): amplifier update fails with [WinError 5] Access is denied on module cache directories

Description

amplifier update fails on Windows when clearing cached module directories. Every module cache entry fails to clear, and all bundle updates subsequently fail. Occurs on both normal updates and --force updates.

Error Output

Could not clear ...amplifier-module-context-simple-...: [WinError 5] Access is denied:
'...\.git\objects\pack\pack-....idx'
Could not clear ...amplifier-module-hooks-logging-...: [WinError 5] Access is denied: ...
... (repeats for all modules)

⚠ Update completed with errors
  ✗ Bundle: amplifier: [WinError 5] Access is denied: ...
  ✗ Bundle: browser-tester: [WinError 5] Access is denied: ...
  (all bundles fail)

Root Cause

Git pack files (.git/objects/pack/*.idx, .pack) are created read-only on Windows. Python's shutil.rmtree() does not handle read-only files on Windows.

Affected components:

• amplifier-app-cli: cache_management.py, module_cache.py, reset.py, sources_compat.py
• amplifier-foundation: sources/git.py (bundle cache clearing)

Fix

• microsoft/amplifier-app-cli#152
• microsoft/amplifier-foundation#137

Start with cache_management.py, module_cache.py, reset.py, and sources_compat.py in amplifier-app-cli, then inspect sources/git.py in amplifier-foundation. Run amplifier update and amplifier update --force on Windows to reproduce the read-only Git pack-file failures. Done means module and bundle caches clear successfully and both update modes complete without errors; the referenced PRs describe the existing fixes.