Simplify and harden the Rust control plane

[areshand]

Summary

• centralize typed authority routing, shared state primitives, and crash-safe writes
• preserve solver workflow budgets and reject incomplete handoffs
• require concrete positive/negative embedding contracts and route integration evidence
• allow supervisor-sealed reviewer rechecks to supersede stale verdicts with audit history
• atomically supersede invalid reviewer findings and TODOs with exact-diff sealed evidence

Safety properties

• one writer lease per workspace
• immutable original task and contract evidence bound to candidate diffs
• incomplete, stale-hash, or unreviewed candidates cannot submit
• the orchestrator cannot forge reviewer evidence or bypass completion

Validation

• Rust unit, lifecycle, integration, and malicious-orchestrator tests passed
• SWE-Bench Pro first 10 at f0190c4: 7/10; rows 0–6 passed and rows 7–9 matched the zero baseline
• evaluation traces: /private/tmp/swe-bench-pro-f0190c4-first10-final/traces

This PR is intentionally a draft. Do not merge without explicit approval.