✨ Edge: graduate Portwing edge mode with cross-repo fleet soak

[scttbnsn]

Goal

Graduate the Drydock portwing/1.0 edge endpoint from opt-in early access.

Acceptance criteria

• A reproducible cross-repository harness runs a realistic multi-agent fleet against Drydock.
• It covers reconnect storms, sustained concurrent exec sessions, and controller-side slow-consumer/backpressure behavior.
• The harness records pass/fail evidence and bounded resource-growth thresholds in CI artifacts.
• Drydock enables the endpoint by default while retaining an explicit emergency disable.
• Portwing and Drydock current docs stop describing edge mode as experimental.
• No ruleset bypasses are used; both repositories pass their normal protected-branch checks and reviews.

[scttbnsn]

Completed by Portwing PR #71 and Drydock PR CodesWhat/drydock#630. The cross-repo fleet soak now gates multi-agent reconnect, exec/log streaming, controller backpressure, and memory budgets; Drydock 1.6 enables the edge controller by default with the documented emergency disable.