[docs] Make Quickstart container checks explicit

[wuchong]

Purpose

Linked issue: close #4433

Make Quickstart startup verification easier to interpret. A plain docker compose ps table can make failed or missing containers easy to overlook, especially when the stack also has services that are expected to exit.

Generative AI disclosure: Yes — Codex (gpt-5).

Brief change log

• Count the expected long-running containers in each Docker Compose Quickstart.
• Document the expected count for each stack.
• Exclude the one-shot rustfs-init and interactive sql-client services where appropriate.
• Point users to docker compose ps -a when the count is lower than expected.

Tests

• ./mvnw -N -B verify spotless:check
• npm run typecheck
• CI=true npm run build -- --no-minify
• Parsed all six embedded Compose definitions with docker compose config --no-interpolate --services.

API and Format

No API or storage format changes.

Documentation

This is a documentation-only change.