Add safe bank failure diagnostics for T5 and T6

Address #14 with request correlation, bounded parser reasons, startup version reporting, and rate-limited storage and settlement logs. Preserve accounting and API identity contracts, extend portable tests, and update release versions and rollout guidance.

t5/plugins/README.md

@@ -109,3 +109,23 @@ decisions and strict response validation for the new bank script. Build and
 install the DLL, then restart the full process. No upstream pins or external
 dependencies changed. See [bank setup and recovery](../../README.md#player-bank-t5-and-t6).
 Portable checks: `python3 tools/test_plugin_bank.py`.
+
+## Bank diagnostics (TWS 1.2.0)
+
+`bankVersion()` returns the loaded DLL's TWS component version, independently of
+upstream pins and the native loader's unchanged `plugin_version()` value.
+`bankResponse()` now also returns `reason`: `ok` on success, otherwise one of
+`empty_body`, `body_limit`, `invalid_json`, `schema`, `field_limit`, `state`,
+`amount_range`, `ok_state`, `missing_id`, or `zero_transfer`. Invalid responses
+clear all parsed fields. Existing acknowledgment acceptance rules are unchanged.
+The returned `code` on valid responses remains API data; bank scripts allowlist
+it before logging. Callers must never log arbitrary response fields.
+
+Native journal logs name load/write/remove, limit identical failures to one
+per 30 seconds, and log recovery with suppressed counts. Exception text, journal
+contents and credentials are excluded. The new scripts require this DLL even
+when disabled by dvar because `bankVersion()` must link. No new third-party
+dependencies or upstream pin changes are required. Rebuild/install the DLL and
+restart the full server process; see the [diagnostic rollout](../../README.md#bank-diagnostics--tws-14).
+Portable checks: `python3 tools/test_plugin_bank.py` executes the real parser,
+storage and native registration adapter with sanitizers and engine shims.