revert(weave): remove persisted agent dashboard type

[bcsherma]

Summary

• Revert feat(weave): add persisted agent dashboard object type #7534.
• Remove the persisted AgentDashboard builtin object schema, registry entry, generated schema, and its tests.
• Keep the backend schema aligned with the frontend rollback in wandb/core#49422.

Validation

• Focused builtin-object compatibility test passes
• Ruff passes
• No remaining AgentDashboard or agent_dashboard references
• Clean diff check

[bcsherma]

• revert(weave): remove persisted agent dashboard type #7673 👈 (View in Graphite)
• master

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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