[metalagman]

Summary

• consume released go-adk-acpagent/v2 v2.7.0 without replace
• adapt ACP exact-session Inspect, ValidateModel, and ChangeModel into the provider-neutral SessionControl port
• preserve all certainty classes with bounded diagnostics; keep context fast-forward unsupported
• advertise control only from an actual ACP control source while pool and Agent-only products remain nil-control
• preserve lazy ACP startup, legacy Build, exact Agent value, and Product lifecycle ownership

Verification

• go test ./... (pass)
• focused ACP integration tests under race (pass)
• go tool golangci-lint run ./... (pass)
• git diff --check (pass)
• independent Prism review: approve

Note

The full local race command can intermittently trip unchanged 25-40ms MCP timing fixtures; the previous PR's upstream full race and three-platform MCP lifecycle checks passed. This PR's upstream checks are authoritative.