fix(tag-manager): require enabled plugin for sley tag commands

[indaco]

Description

All sley tag subcommands (create, list, push, delete) now require tag-manager.enabled: true in .sley.yaml. Previously, sley tag create would print a warning but proceed with default settings - this warn-and-continue behavior was confusing and inconsistent.

Changes:

• Add a Before hook on the parent tag command that gates all subcommands behind enabled: true, returning a clear error with setup instructions
• Remove the warn-and-fallback block from runCreateCmd
• Rename IsEnabled() to IsAutoCreateEnabled() on TagManagerPlugin for consistency - every other plugin's IsEnabled() checks only Enabled, but this one checked Enabled && AutoCreate

Related Issue

Fixes #211

Notes for Reviewers

• None