docs: refine CLI roadmap scope

[rhnvrm]

Summary

• reframe v0.12.0 as a single practical first CLI release instead of an implied mc-style full feature surface
• clarify the core command/flag set, config/auth work, and internal execution order for the release
• move v1.0.0 emphasis to stability, docs, tests, and validation of the command set defined in v0.12.0

Details

The updated roadmap keeps one v0.12.0 release, but narrows it to a realistic first CLI:

• config/auth (AWS_*, --region, --profile, ~/.aws/credentials)
• s3:// parsing plus local path handling
• core commands: ls, cp, rm, mb, rb, mv, presign, sync
• core flags: --recursive, --dry-run, --json, --delete, --exclude, --include
• thin library-backed flags where the library already makes them cheap

It also calls out explicit non-goals for the initial CLI roadmap so the project does not drift toward minio/mc parity.