Subplan 02 Slice 2 foundation. vendor/sqlite/ holds the amalgamation
(provenance + upgrade notes in its README); make build compiles it into
build/vendor/libsqlite3.a (statically linked into dist via -L) and
build/vendor/jit/libsqlite3.dylib (dlopen'd by sx run via tests/run.sh's
-L flag) — separate directories because the macOS linker prefers a dylib
over an archive in one search dir.
The sx JIT resolves #foreign symbols via dlsym(RTLD_DEFAULT), where the
already-loaded OS libsqlite3 wins by load order — so the vendored build
renames its API to dist_sqlite3_* (vendor/sqlite/rename.h, -include'd),
making resolution unambiguous in both modes: those symbols exist only in
the vendored products.
src/db/sqlite.sx binds the renamed surface behind Sqlite/SqliteStmt
(open/exec/prepare/bind/step/column/finalize, errmsg, last_insert_rowid,
changes, libversion); opaque handles cross the FFI as usize, strings
read from sqlite are copied before its buffers die.
make test 20/20 (new: sqlite_smoke.sx — pins the loaded version to the
vendored 3.53.2, round trip, reopen persistence, BEGIN/ROLLBACK, errmsg;
also verified as an AOT binary with no libsqlite3 in otool -L).
