[BUG] --force overwrites preserved files when rsync is unavailable

[c-vigo]

Description

Running install.sh with --force should preserve user files listed in PRESERVE_FILES (including README.md and CHANGELOG.md).
When rsync is not available in the container, the fallback copy path overwrites those files anyway.

Steps to Reproduce

1. Use an image/environment where rsync is not installed.
2. In an existing workspace, customize README.md and CHANGELOG.md.
3. Run:
   install.sh <workspace> --version dev --skip-pull --force --org vigOS
4. Observe init output:
   Warning: rsync not available, preserved files may be overwritten
5. Check README.md and CHANGELOG.md.

Expected Behavior

Files in the preserve list are never overwritten during --force, regardless of copy backend.

Actual Behavior

Preserved files are overwritten when fallback copy is used (no rsync).

Environment

• OS: Linux
• Container Runtime: Podman
• Image Version/Tag: ghcr.io/vig-os/devcontainer:dev
• Architecture: amd64

Additional Context

The init output lists preserved files correctly before copy, but fallback logic does not enforce preservation.

• TDD compliance (see .cursor/rules/tdd.mdc)

Possible Solution

• Add rsync to the image to use the primary safe copy path.
• Keep fallback logic preserving files explicitly for robustness.
• Add regression coverage for fallback behavior.

Changelog Category

Fixed