fix(bus): bind replies to expected responders

[hartsock]

What this PR does

• Stores the expected responder fingerprint with every reply waiter for both resolved and direct routes.
• Rejects an authenticated wrong-signer reply without consuming the waiter or mutating replay state, then rechecks identity atomically when delivering the reply.
• Preserves nonce/sequence handling for unknown replies and malformed signed payloads.
• Intentionally stacks on security(bus): make authenticated peer provenance mandatory at the Transport/Inbound seam #79 so sender fingerprints are verified before correlation admission; merge security(bus): make authenticated peer provenance mandatory at the Transport/Inbound seam #79 first, then retarget this PR to main.

Closes #80

Test plan

• CARGO_TARGET_DIR=/private/tmp/agent-mesh-target-80 just check
• CARGO_TARGET_DIR=/private/tmp/agent-mesh-target-80-cov just cov-ci (75% floor)
• Added deterministic tests for resolved/direct routes, wrong-then-right replies, copied-nonce poisoning, timeout/late/duplicate/unknown/cancel/receiver-drop behavior, and malformed-payload replay semantics.

Out of scope

• Automatic waiter cleanup when the entire request* future is externally dropped; explicit send-failure, timeout, and cancellation paths remain covered.
• Any relaxation of security(bus): make authenticated peer provenance mandatory at the Transport/Inbound seam #79's direct carrier/signer policy or new relay authorization.

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