[v0.91.8][runtime-v3][protocols] Implement real Provider, ACIP, A2A, and Cloud Bridge adapters

[danielbaustin]

Outcome\nImplement the four external-facing Runtime v3 adapter contracts as real Rust/Tokio integrations.\n\n## Scope\n- Provider dispatch with bounded timeout, cancellation, retry, and authenticated identity\n- ACIP bidirectional exchange contract\n- A2A authenticated message exchange\n- Cloud Bridge transport with explicit capability and failure semantics\n- Rustls/mTLS configuration where transport is networked\n- deterministic local black-box tests and end-to-end integration proofs\n\n## Acceptance\n- No in-process receipt-only or degraded production substitute\n- No plaintext credentials or credential material in tracked artifacts\n- Real authenticated request/response or message exchange\n- Fail-closed malformed, unauthorized, timeout, replay, and shutdown cases\n- FastWork validation, strict Clippy, and exact pre-PR review\n- Must integrate after #5657 closes and before WP-12 cutover\n\n## Non-goals\nAWS provisioning and cloud account experiments are excluded.

[danielbaustin]

Shared constraint: no parallel homemade transport stack. Reuse existing Tokio/Axum/Rustls/COTS boundaries, remove superseded receipt/degraded paths, and record before/after physical LoC with a net-reduction target.