Migrate Prepper to Spring Shell 4

[arnabnandy7]

Context

The Embabel Agent Spring Shell 4 upgrade tracked in embabel/embabel-agent#1720 removes the legacy Spring Shell annotation API used by Prepper.

Validating Prepper against Embabel Agent 1.5.2-SNAPSHOT currently requires corresponding downstream API migrations.

Required changes

• upgrade Prepper to the compatible Embabel Agent snapshot
• replace legacy ShellComponent and ShellMethod annotations with the Spring Shell 4 command API
• update relocated Actor and AgentInvocation APIs
• replace the removed ProcessOptions builder usage
• update relocated test-support APIs

Verification

• compile against the locally installed Embabel Agent 1.5.2-SNAPSHOT
• run the Prepper unit test suite with integration tests disabled
• launch the interactive shell and verify the prep command is registered

Related upstream issue: embabel/embabel-agent#1720