feat(iteration-41): preserve offline fake CTP actor contracts

backtrader_runtime/_local_fake_account_actor_candidate/LOCAL_FAKE_ONLY.md

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+# Local fake-only account actor protocol candidate
+
+This package is an isolated integration candidate. The service child owns a
+SQLite ledger and in-memory fake sink; the caller sends typed intents over
+local stdio JSON-lines and receives an unauthenticated local receipt. The
+runtime registry, CLI, default runtime imports, and `BtApiStore` do not import
+or construct this candidate.
+
+Response lines and aggregate queued output are bounded. Outgoing requests are
+capped at 64 KiB and use a write deadline. If shutdown requires forced child
+termination, the client closes its streams and reports
+`actor_service_cleanup_uncertain`: no OS Job Object or process-group supervisor
+verifies descendant cleanup.
+
+The child and caller share one OS principal; the SQLite file is locally
+writable. Snapshot proof, account/session values, epochs, and fake sends are
+synthetic. This package contains no provider, credential, network, native SDK,
+external actor identity, cross-host writer fence, or real account snapshot.
+`StoreBoundaryHarness` is a toy ordering model; it does not import or modify
+`BtApiStore`. The candidate is not registered, not a Store route, and not write
+authority. G6-P/F14 remain unresolved; `NO_WRITE / LIVE_NO_GO` is unchanged.

backtrader_runtime/_local_fake_account_actor_candidate/__init__.py

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+"""Unregistered local fake-only account-actor protocol candidate.
+
+Nothing is imported here. The runtime registry, CLI, and Store do not import
+this package, and importing :mod:`backtrader_runtime` never loads it.
+"""