Add store-slatedb: a SlateDB tuple-store module

[maxweber]

Summary

The first non-default dbval.store backend — SlateDB, an embedded ordered key-value store on object storage (S3/GCS/local fs) — ported from slateval's storage layer into a submodule:

store-slatedb/
  deps.edn                        ; depends on dbval via :local/root ".." + slatedb-uniffi
  src/dbval/store/slatedb.clj     ; the adapter (~130 lines)
  test/dbval/store/slatedb_test.clj

Stacked on #7 (tuple-store); retarget after it merges. Step 3 of the storage-protocol plan — after this, slateval's remaining delta is its temporal features (as-of/since/history), not storage.

Why a module (unlike the SQLite adapter)

dbval.store.slatedb :imports io.slatedb.uniffi classes, so the namespace cannot load without the jar — no requiring-resolve trick available — and slatedb-uniffi is a heavy native dependency. Consumers use it as a git dep with :deps/root "store-slatedb"; SQLite/memory users never download it.

Why the adapter is thin

SlateDB's WriteBatch is write-only — no read-your-writes — which is exactly the case the engine's pending-overlay design (from #7) was built for. The adapter only provides:

• -scan: scanWithOptions over a KeyRange, with SlateDB's native descending iteration for reverse scans
• -commit!: stage keys (empty values) into a WriteBatch, one atomic .write
• plus the JNA native-library extraction workaround for the uniffi loader, taken verbatim from slateval

Notably, slateval independently evolved its own pending-writes overlay merged into slice when it ported to SlateDB — the engine-owned overlay in #7 is that same solution, generalized so every backend gets it for free.

Tests

• Module suite (cd store-slatedb && clojure -M:test) runs the same representative flows as dbval.test.store — transact, upsert, retract history (forward + reverse scans), query, pull, index-range, snapshot isolation, failed-transaction atomicity — against SlateDB over the memory:/// object store: 2 tests, 11 assertions, 0 failures.
• Root suite unchanged: 162 tests, 1048 assertions, 0 failures.
• CI runs the module tests as a second step.

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https://claude.ai/code/session_014dX8tTR4yFh5SyBGw3atpo