sqlite: SAFETY comments on the substrate UDF get_connection blocks (D-40)

Review 004 item 15: the unsafe { ctx.get_connection() } UDF blocks
carried no SAFETY justification. Added the concrete soundness
invariant at all ten sites (the eight attach_alkstore_functions
registrations, the notify registration, the test-module savepoint
probe — same class) and registered the comment-only change as
PROVENANCE delta D-40 per ADR-012 §3's diff-fidelity posture.

Task: sqlite-substrate-safety-comments

tasks/sqlite-substrate-safety-comments.md

@@ -1,7 +1,7 @@
 ---
 id: sqlite-substrate-safety-comments
 name: SAFETY comments on the substrate UDF blocks, riding a PROVENANCE delta (review 004 item 15)
-status: pending
+status: completed
 depends_on: []
 scope: narrow
 risk: low
@@ -64,8 +64,33 @@ if not, leave them and record why.
 
 ## Notes
 
-> To be filled by implementation agent
+- Same-class neighbors **included**: `schema.rs:104` (the `notify`
+  registration in `attach_notify`) and `ops.rs`'s test-module scalar
+  probe (`a_panicking_savepoint_body_leaves_no_frame_on_the_scalar_path`)
+  are the identical rusqlite UDF shape — registered on one connection,
+  invoked only synchronously inside that connection's statement
+  evaluation — so both joined the delta; all **ten** sites carry the
+  comment.
+- The comment states the concrete invariant, derived from rusqlite
+  0.40's `Context::get_connection` contract (functions.rs; the issue
+  #643 analysis behind its unsafety): the rebuilt `ConnectionRef`
+  could alias a cross-thread access or outlive the callback — neither
+  reachable here (each connection one-thread-at-a-time: rusqlite
+  `Connection` is !Sync, the reader pool transfers owned connections,
+  the writer lease is exclusive; the closure consumes the deref'd
+  reference only within the callback's lifetime).
+- Delta registered as **D-40** in `PROVENANCE.md`, category `hygiene`
+  (comment-only, zero behavior change) — the deliberate exception to
+  D-15's comment elision, riding a delta per ADR-012 §3.
 
 ## Summary
 
-> To be filled on completion
+Added uniform `// SAFETY` comments at all ten `unsafe {
+ctx.get_connection() }` UDF sites (the eight review-scoped blocks in
+`attach_alkstore_functions`, plus the same-class `notify` registration
+and the test-module savepoint-panic probe) and registered the
+comment-only change as PROVENANCE delta D-40. Verified: `cargo test`
+workspace green (alkstore-sqlite 203 passed, all crates green
+unchanged), `cargo clippy --all-targets -- -D warnings` clean,
+`cargo fmt --check` clean, `cargo build` green, fuzz gate
+(`fuzz/shared`) green — comment-only diff, no behavior change.