Claimant-Aware Assignment Race Fence

[mfethe1]

Parent

#3

What to build

Add claimant-aware Fleet Controller assignment so the host that wins the claim is the host that receives the assignment, with command-ref and task-lease conflicts returned deterministically to losing claimants.

Acceptance criteria

• Rosie and Lenny racing on the same message produce exactly one task publish.
• A claim from Lenny assigns Lenny when Lenny is eligible, even if Rosie sorts first in host inventory.
• A claimant outside delivery scope cannot steal work.
• Existing explicit /assign command replay tests still pass.

Blocked by

• Claimable Telegram Work Promotion #5