plugin crate: register the store on the cold lane busbar boots stores through

README.md

@@ -56,10 +56,12 @@ this repository's `store-sqlite/` directory. The
 `store-sqlite-plugin` crate is deliberately tiny: the logic crate also holds
 its one door (`door::door`, the store v3 table over `SqliteStore` through
 `busbar_contract::store_door!`; its `open` slot adapts the operator's settings
-into a `SqliteStore`), and the plugin crate exports that door as the image's one
-symbol, `busbar_plugin_door` (`export_door!`), so the cdylib answers the loader
+into a `SqliteStore`), and the plugin crate exports that door as
+`busbar_plugin_door` (`export_door!`), so the cdylib answers the loader
 through the same door a busbar build that LINKS `busbar-store-sqlite`
-registers — one source, both doors.
+registers — one source, both doors. The plugin crate also registers the store
+on the cold store lane (`export_store_plugin!`) that the busbar kernel at the
+pin boots a configured `store:` through.
 
 
 - The **default durable store** for busbar's governance data: virtual

store-sqlite-plugin/src/lib.rs

@@ -8,18 +8,38 @@
 //! All the store lives in the `busbar-store-sqlite` crate, including its one door
 //! (`busbar_store_sqlite::door::door`, the store v3 table). This crate re-exports the logic crate,
 //! so the library it builds carries exactly the code a busbar build links, and exports that door as
-//! the image's ONE symbol, `busbar_plugin_door` (`export_door!`, unconditionally) — one source,
-//! both doors (DECISIONS #2 rule (1)).
+//! `busbar_plugin_door` (`export_door!`, unconditionally) — one source, both doors (DECISIONS #2
+//! rule (1)). It also registers the store on the cold store lane the busbar kernel at the pin boots
+//! a configured store through (`cold`, `export_store_plugin!`).
 //!
-//! This crate is `deny`, not `forbid`: the export macro's `#[unsafe(no_mangle)]` is the one reviewed
-//! exemption (a `forbid` cannot be lifted for it). No other `unsafe` exists here.
+//! This crate is `deny`, not `forbid`: the two export macros (`#[unsafe(no_mangle)]`, the cold
+//! boundary's `unsafe extern` functions) are the reviewed exemptions (a `forbid` cannot be lifted
+//! for them). No other `unsafe` exists here.
 
 #![deny(unsafe_code)]
 
 pub use busbar_store_sqlite::*;
 
-/// The exported door: the macro's `#[no_mangle]` symbol is the one exemption.
+/// The exported door: the macro's `#[no_mangle]` symbol is an exemption.
 #[allow(unsafe_code)]
 mod exported {
     busbar_contract::export_door!(busbar_store_sqlite::door::door);
 }
+
+/// The store a busbar at the pin BOOTS. Its kernel opens a configured dropped-in store through the
+/// cold store lane (`PluginRegistry::open_store` -> `load_store_image`: `busbar_abi`,
+/// `busbar_plugin_kind`, `busbar_open`, ...), not through the door; an image that exports only
+/// `busbar_plugin_door` answers `busbar_plugin_kind` with NULL there and the boot is refused
+/// (BUSBAR-9007 "returned a null kind string"). This registration answers that lane over the same
+/// [`SqliteStore`], opened by the door's own settings parser ([`door::open`]).
+fn open_cold(cfg: &str) -> Result<busbar_contract::abi::sdk::StoreHandle, String> {
+    door::open(cfg).map(|s| Box::new(s) as busbar_contract::abi::sdk::StoreHandle)
+}
+
+/// THE COLD LANE's registration (`export_store_plugin!`): the contract SDK's frozen symbols answer
+/// through it. The macro's boundary functions are `unsafe extern "C-unwind"` by the cold ABI's own
+/// definition, and it registers through a load-time initializer section — the other exemption.
+#[allow(unsafe_code)]
+mod cold {
+    busbar_contract::abi::sdk::export_store_plugin!(super::open_cold);
+}