[Plugin Pack Child] Second Wave Execution Spec & Delivery

[ashleyshaw]

Child of #732. Define and execute second-wave plugin pack tasks with manifest parity, acceptance criteria, and validation gates.

---

Definition of Ready (DoR)

• Task described and scoped
• Estimate added if relevant

Definition of Done (DoD)

• Task completed and documented
• Changelog entry prepared for PR
• PR uses correct branch prefix

[linear-code]

LS-873