chore(deps): normalize engines' dev-dep tokio features (review 004 item 16)

All three engines' [dev-dependencies] tokio now carry the same feature
set: rt-multi-thread + macros + time + test-util (previously sqlite had
rt-multi-thread+macros+time, pg test-util only, mem rt+macros).
Dev-dep metadata only; each engine's tests verified green plus the
workspace build/clippy/fmt gates.

tasks/normalize-tokio-dev-deps.md

@@ -1,7 +1,7 @@
 ---
 id: normalize-tokio-dev-deps
 name: Normalize the engines' dev-dep tokio feature sets (review 004 item 16)
-status: pending
+status: completed
 depends_on: []
 scope: single
 risk: trivial
@@ -43,8 +43,23 @@ change.
 
 ## Notes
 
-> To be filled by implementation agent
+<!-- implementation decisions of record -->
+
+The union picked exactly matches the task's expectation:
+`rt-multi-thread + macros + time + test-util` — the pg engine's
+dev-dep `test-util` coverage is preserved, no engine's tests needed
+anything beyond the union, and no code change was required anywhere.
 
 ## Summary
 
-> To be filled on completion
+Normalized all three engines' `[dev-dependencies]` tokio feature sets
+to `["rt-multi-thread", "macros", "time", "test-util"]` (previously:
+sqlite `rt-multi-thread+macros+time`, pg `test-util`, mem `rt+macros`)
+— dev-dep metadata only, no published-surface or runtime-dep change.
+
+Verified (2026-10-11): workspace `cargo build`, `cargo clippy
+--all-targets -- -D warnings`, `cargo fmt --check` all clean;
+`cargo test -p` green for alkstore-mem (102 unit + 26 ct),
+alkstore-sqlite (203 unit + 26 ct + 1 doc), alkstore-postgres
+(135 unit + 26 ct + 9 integration, full target incl. the server-less
+SKIP posture).