Use compose file argument in docker compose down command

[Copilot]

The install script was calling docker compose down without specifying which compose file to use, potentially bringing down the wrong services when switching between sample applications that use different compose files (smart-intersection uses compose-scenescape.yml, others use compose-without-scenescape.yml).

Changes

• Introduced RI_COMPOSE_FILE_ARG variable to store the appropriate compose file path based on SAMPLE_APP
• Updated docker compose commands to use -f "$RI_COMPOSE_FILE_ARG" flag for both ps and down operations
• Moved compose file determination before the docker compose down command instead of after
• Added validation for both SAMPLE_APP and compose file existence

# Before
docker compose down

# After
if [ "$SAMPLE_APP" = "smart-intersection" ]; then
    RI_COMPOSE_FILE_ARG="compose-scenescape.yml"
else
    RI_COMPOSE_FILE_ARG="compose-without-scenescape.yml"
fi

docker compose -f "$RI_COMPOSE_FILE_ARG" down

This ensures the correct services are brought down when switching between sample applications.

Original prompt

Work on TODO: run docker compose down with RI_COMPOSE_FILE_ARG as source of docker compose yaml (from metro-ai-suite/smart-traffic-intersection-agent/setup.sh)

Created from VS Code via the GitHub Pull Request extension.

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