[Feature]: Add a `down` alias to `workspace delete` to align with `docker compose down`

[yosimasu]

Before submitting

• I have searched existing feature requests and discussions to confirm this has not been requested

Problem or motivation

Devsy's workspace lifecycle already lines up closely with docker compose: devsy workspace up ≈ docker compose up, devsy workspace stop ≈ docker compose stop. The one gap is teardown. devsy workspace delete (alias rm) walks a workspace through the running → stopped → deleted lifecycle, which is exactly what docker compose down does. Users coming from Compose reach for devsy workspace down and it doesn't exist, so the mental mapping breaks at the last step.

Proposed solution

Add down as an alias of the existing workspace delete command (which already carries the rm alias). This keeps the Compose mental model intact (up / stop / down) without breaking anyone currently using delete or rm. No behavior change — down simply invokes the same command.

Alternatives considered

• Rename delete → down: rejected — breaks existing scripts and muscle memory (delete / rm).
• Do nothing / rely on docs: users still hit friction when the obvious Compose verb is missing.
• How other tools handle it: docker compose uses up / down; adding the alias makes Devsy match that convention while keeping delete as the canonical name.

Area

CLI

Acceptance criteria

• devsy workspace down [workspace] behaves identically to devsy workspace delete [workspace]
• down appears as an alias in devsy workspace delete --help / command help output
• Shell completion suggests down
• Existing delete / rm usage is unchanged