[BUG] Fix State Validation Missing in Tagged Power Operations (start-tagged, stop-tagged, reboot-tagged)

[ditahkk]

Description:
Tagged operations (start-tagged, stop-tagged, reboot-tagged) fail on invalid instance states.

Fix:

• Add state validation to parallel execution
• start-tagged requires "stopped"
• stop/reboot-tagged require "running"
• Skip invalid instances

Files Changed:

• ssm_power.go, ssm_power_test.go, manager.go, manager_test.go, go.mod, go.sum

Acceptance Criteria:

• State validation works
• Tests pass
• Linter passes
• Dependencies updated

Testing:

• start-tagged only starts stopped instances
• stop-tagged only stops running instances
• reboot-tagged only reboots running instances
• Fail gracefully on invalid states
• Parallel execution verified