fix: tear down docker e2e integration stack by default

[NeerajCodz]

Motivation

• The E2E PowerShell script started the Docker Compose integration stack by default but did not stop it, leaving host-published development services and hard-coded dev credentials exposed after the run.
• The change aims to reduce accidental network exposure of unauthenticated or default-credential services started by the script while preserving the ability to opt out of teardown.

Description

• Track whether the script started the compose stack with a new $startedStack variable set to -not $SkipStart.
• Wrap the main E2E workflow in a try/finally block so cleanup runs even if the script fails mid-run.
• In finally, run docker compose -f docker-compose.integration.yml down when the script started the stack and -KeepRunning is not set, and preserve -KeepRunning behavior when explicitly provided.

Testing

• Verified the change locally by inspecting the file diff with git diff -- scripts/e2e-docker.ps1 and committing the update, and those repository checks completed successfully.
• No integration/runtime tests were executed in this environment because Docker and PowerShell were not available, so runtime teardown behavior was not executed here; CI should exercise the script in an environment with Docker/PowerShell.

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Codex Task