rholang: add opt-in split LogicT post-match execution runtime with persisted continuations

[machieke]

Summary

This PR merges asi/experimental/logicT-execution-runtime into origin/rust/dev and introduces an experimental, opt-in split execution runtime for post-match continuation processing in Rholang.

The new runtime path is gated by SplitPostMatchConfig.enabled and remains disabled by default, preserving existing behavior unless explicitly enabled.

Diff size: 15 files changed, +5555 / -279.

Why

Post-match continuation execution currently runs in a single flow. This change introduces a deterministic step-based model that can:

• bound execution by step gas limits
• persist suspended execution state
• resume execution safely with optimistic version checks
• support executor-facing continuation queues and bridge-specific scheduling hooks

What changed

1. Split post-match execution model (feature-gated)

• Added explicit post-match execution state and control states.
• Added internal reduce_step(exec_state, gas_limit) stepping with terminal outcomes:
  • Completed
  • Suspended
• Added compatibility path for full execution and equivalence coverage.

2. Continuation persistence layer

• Added dedicated in-memory continuation store with lifecycle support:
  • create, load, update, complete, expire, fail
• Persisted continuation schema includes:
  • handle (origin + nonce)
  • serialized state
  • per-step gas limit
  • funding policy and visibility
  • optional bounty and TTL-derived expiry
  • subtype metadata (Standard / Bridge)
  • status, version, state root, storage bytes
• Added optimistic concurrency/version mismatch protection.
• Added snapshot/restore support for recovery validation.

3. Runtime continuation APIs

• Added reducer APIs for continuation management and execution:
  • queue/list/load/epoch-expiry operations
  • execute_continuation
  • execute_public_continuation
  • bridge execution helpers:
    • queue by deadline / reward
    • rescue candidates
    • phase updates
    • execute-next scheduling hooks

4. Funding, visibility, and bridge subtype support

• Added:
  • FundingPolicy::{ProducerOnly, ExecutorPays}
  • ContinuationVisibility::{Private, Public}
  • bridge metadata/finality/reward policy structures
• Public executor flow enforces eligibility checks (public + executor-funded).
• Bridge queue ordering supports deadline and reward priority paths.

5. Operational hardening and observability

• Added continuation safety caps:
  • max serialized state size: 128 KiB
  • max branch fan-out: 128
• Added deterministic epoch-based expiry sweeps.
• Added continuation and bridge metrics for creation, resume outcomes, gas-per-step, expiry, and queue/execute requests.

6. Tests

• Expanded reducer and integration coverage for:
  • split enabled/disabled behavior
  • deferred follow-up persistence + resume semantics
  • stale version / invalid handle rejection
  • deterministic replay/idempotent retry behavior
  • public executor policy enforcement
  • private/TTL expiry behavior
  • bridge metadata/queue ordering/scheduler hooks
• Added continuation store tests for:
  • serialization round-trip and tamper detection
  • versioning and state-root transitions
  • storage accounting
  • expiry and epoch regression
  • snapshot/restore behavior