Fix the Docs build and address review

Three things, from CI and from review on #42.

Docs (CI failure)
-----------------
`RUSTDOCFLAGS="-D warnings" cargo doc` rejected
`[`UnifiedMemory`](crate::store::UnifiedMemory)` as a redundant explicit
link target -- the type is already imported at the top of this module, so
the bare form resolves on its own. A reference definition would have been
redundant for the same reason, so there is none.

`DriverRegistry::builtin` rustdoc (CodeRabbit)
---------------------------------------------
Valid: the doc still enumerated "the null placeholder, TinyCortex, and the
three supported native HTTP engines" after this PR added a fifth reserved
id. A registry whose doc does not list what it reserves is exactly the
drift the doc exists to prevent.

Lint scope (CodeRabbit)
-----------------------
Narrowed rather than removed. `expect_used` is `warn` workspace-wide
(Cargo.toml) and CI runs clippy with `-D warnings`, and `expect`'s message
is the failure diagnostic in a conformance test -- converting these to
`Result` would trade a named assertion for an anonymous `?`. Eight files
in this workspace carry the same attribute, including the sibling
`conformance_test.rs` this one is modelled on.

The finding did surface something real though: this file has seven
`expect` calls and no explicit `panic!`, so `clippy::panic` was never
needed. Dropped, leaving this file stricter than its siblings.

cargo fmt --all -- --check: clean
RUSTDOCFLAGS="-D warnings" cargo doc --no-deps --all-features -p tinymemory-core: clean
cargo test -p tinymemory-core --lib store::factories_provider_test: 5 passed

Author: YellowSnnowmann

core/src/store/factories.rs

@@ -357,7 +357,7 @@ pub fn create_memory(
 /// engine in the workspace is bound.
 ///
 /// Issue #18 §A3/§A5. Until this existed, `tinymemory-core`'s
-/// [`UnifiedMemory`](crate::store::UnifiedMemory) was the one storage
+/// [`UnifiedMemory`] was the one storage
 /// implementation in the workspace with no route through the contract: the
 /// TinyCortex adapter binds the bundled engine, `adapters/remote` binds the
 /// three hosted services, and core's own SQLite store was reachable only by

core/src/store/factories_provider_test.rs

@@ -6,7 +6,12 @@
 //! no way to express it as a driver at all — which is precisely the gap §A3
 //! describes. These are the missing equivalents.
 
-#![allow(clippy::expect_used, clippy::panic)]
+// `expect` is the assertion mechanism here, and its message is the failure
+// diagnostic — `expect_used` is `warn` workspace-wide (Cargo.toml) and CI runs
+// clippy with `-D warnings`. Scoped to that one lint: unlike the sibling
+// conformance tests this file has no explicit `panic!`, so it does not need
+// `clippy::panic` too.
+#![allow(clippy::expect_used)]
 
 use std::sync::Arc;
 

src/registry/mod.rs

@@ -186,8 +186,9 @@ impl Default for DriverRegistry {
 }
 
 impl DriverRegistry {
-    /// The registry every host starts from: the null placeholder, TinyCortex,
-    /// and the three supported native HTTP engines.
+    /// The registry every host starts from: the null placeholder, the two
+    /// embedded engines — TinyCortex and this workspace's own `namespace`
+    /// store — and the three supported native HTTP engines.
     #[must_use]
     pub fn builtin() -> Self {
         let mut reserved = BTreeMap::new();