Close ECP-7 development after Batch 29

[FatosLocos]

Summary

• add the preregistered Batch 29 late residual-activation intervention
• freeze the residual sender branch through step 30,000 and enable its gradients from step 30,001
• record the sealed negative result and verify all compact evidence hashes
• close ECP-7 development after 29 variants without accessing the confirmatory test
• update the fresh-agent handoff for a separately preregistered ECP-8 phase

Result

Batch 29 exactly matches the Batch 25 trajectory through step 30,000, then reaches 84.74% mean validation and 81.74% worst-link validation after late residual activation. It does not add hard-code capacity, so it fails the registered development gate. ECP-6 remains the latest confirmed result.

Verification

• git diff --check
• .venv/bin/ecp6 --config config/ecp7-b29-development.yaml validate
• .venv/bin/pytest -q (133 passed)
• Batch 29 compact-manifest hashes verified against the local sealed-development artifacts