ADR-013: fold the forked substrate into alkstore-sqlite — no fourth crate

Operator review of ADR-012's fork design re-litigated §1's crate
identity. alkstore-substrate misdescribed what the code is (unpublished,
path-dep-only, one consumer, SQLite-only — not a family-wide substrate);
the mechanical-diff hope was gone at fork time regardless (port deltas,
renames, re-derived half); and the alksocks F-1 lesson applies — a
vendored region under a second, weaker instruction set is a defect seam.
The fork folds into alkstore-sqlite as a bounded module subtree
(src/substrate/); ADR-012 §3–§6 retained verbatim, §2 retained with its
enforcement re-sited from the crate graph to diff fence + review +
contract-suite equivalence pins. OQ-11 item (1) dissolved.

docs/architecture/decisions/001-crate-split.md

@@ -38,9 +38,11 @@ The project ships as a **family of crates**:
    documentation. No driver dependencies. Compile-lean by construction:
    the base crate has no engine machinery to keep out.
 2. **`alkstore-sqlite`** — the SQLite engine implementing the core
-   surface. Single driver: rusqlite + the forked `alkstore-substrate`
-   lineage ([ADR-003]; ownership per
-   [ADR-011](011-sqlite-substrate-fork.md)).
+    surface. Single driver: rusqlite + the forked honker-core
+    lineage, carried in-tree as the engine crate's substrate module
+    subtree ([ADR-003]; ownership per
+    [ADR-011](011-sqlite-substrate-fork.md); folded into the engine
+    crate per [ADR-013](013-fold-substrate-into-sqlite.md)).
 3. **`alkstore-postgres`** — the Postgres engine implementing the core
    surface. Single driver: tokio-postgres + deadpool-postgres
    ([ADR-004]).