Fix malformed shell function aliases in artifacts-helper

[Copilot]

When installing as a non-root user, the shell function shims written to rc files were missing path quoting and argument forwarding, producing dotnet() { /usr/local/share/codespace-shims/dotnet ; } instead of dotnet() { "/usr/local/share/codespace-shims/dotnet" "$@"; }.

Root cause

The ALIASES_BLOCK string contains literal " characters. Embedding it inside bash -c "..." caused the outer shell to misparse the quotes during expansion:

# Broken: embedded quotes in $ALIASES_BLOCK corrupt the bash -c argument
sudo -u ${_REMOTE_USER} bash -c "printf '%s' \"$ALIASES_BLOCK\" >> $TARGET_FILE"

The inner bash received a mangled command where the path quotes and "$@" were consumed as shell syntax rather than literal characters.

Changes

• install.sh: Write ALIASES_BLOCK to a temp file first, then append via cat — eliminating the quoting hazard entirely. Also quotes ${_REMOTE_USER} to prevent word splitting.

_TEMP_BLOCK=$(mktemp)
printf '%s' "$ALIASES_BLOCK" > "$_TEMP_BLOCK"
sudo -u "${_REMOTE_USER}" bash -c "cat '$_TEMP_BLOCK' >> $TARGET_FILE"
rm -f "$_TEMP_BLOCK"

• test_shim_integration.sh: Added checks that alias definitions in rc files include properly quoted paths and "$@" argument forwarding.
• devcontainer-feature.json: Bumped version to 3.0.8.