The wasm driver's `sqlite3_get_autocommit` binding is asserted by cast, not checked

[sirtimid]

Found reviewing #1021 (sirtimid/crank-rollback-integrity).

What

wasm.ts reaches the autocommit binding through an unchecked cast:

sqlite3.capi as Sqlite3Static['capi'] & AutocommitCapi

@sqlite.org/sqlite-wasm's index.d.ts declares CAPI as a generated member list with no index signature and no sqlite3_get_autocommit. The binding does exist in the installed build — but nothing verifies that.

If it is ever absent or renamed, getAutocommit is undefined and every read of inTransaction throws TypeError — from inside beginIfNeeded, commitIfNeeded and rollbackIfNeeded, i.e. the exact machinery #1021 exists to harden. Browser-only, at runtime, with no startup signal.

This is the one place in that diff where an as cast stands in for an unverified assumption about a foreign module, and it is load-bearing: replacing the cached _inTx with a live sqlite3_get_autocommit read is the headline fix of the kernel-store half.

Suggested fix

One line at init turns a scattered runtime TypeError into a clear startup failure:

typeof getAutocommit === 'function' ||
  Fail`sqlite3 capi lacks sqlite3_get_autocommit`;

[sirtimid]

Closing: the cast does not exist on main. The PR that introduces the sqlite3_get_autocommit read will assert the binding is a function at init, as suggested here.