feat(fwdctl/launch): add scenario-driven deploy, list/kill instance management, and dry-run planning (3/4)

[AminR443]

Why this should be merged

This PR upgrades fwdctl launch from deploy/monitor-only into a full lifecycle management tool. It adds planning (--dry-run), managed instance operations (list, kill), and scenario-based launches.

How this works

The launch CLI now supports:

• fwdctl launch list to show ManagedBy=fwdctl instances (with --running / --mine)
• fwdctl launch kill to terminate a specific instance, your instances, or all managed instances
• fwdctl launch deploy --scenario <name> to pick a scenario from benchmark/launch/launch-stages.yaml
• fwdctl launch deploy --dry-run [plan|plan-with-cloud-init] to preview actions without creating resources
• fwdctl launch deploy --follow [follow|follow-with-progress] for log/progress streaming modes

How this was tested

Some UT. mostly manually launching and ensuring all the cases work fine.

Design Notes

1. list/kill are intentionally scoped to ManagedBy=fwdctl resources to avoid accidental operations on unrelated instances.
2. plan-with-cloud-init was added so generated cloud-init can be inspected/reviewed before launch.

[rkuris]

This is a really big PR that will require another pass.

[rkuris]

This is difficult or impossible to review since I can't compare the original script to what you've got here without doing a lot of work. Suggestions welcome.

[AminR443]

I'd suggest doing a dry-run with cloud-init dump so you could inspect the resulting cloud init manually. It'll be a little bit hard still because of progress tracking commands, but you could remove them and then do the comparison.

To do this:

AWS_PROFILE=<your-profile> cargo run --bin fwdctl --features launch -- launch deploy --dry-run=plan-with-cloud-init

You can check this diff to that I generated:
https://www.diffchecker.com/GglAZd0v/

Note: The branch args are not present because I ran the default configuration.

[AminR443]

It's pretty easy to verify with the diff that the original commands are mostly untouched. The rust install changed because one of the original commands had non-successful exit code, couldn't write to the specified directory.