Update vendored SQLite amalgamation to 3.53.2

[stumpylog]

Summary

Updates the vendored SQLite amalgamation from 3.45.3 (2024) to 3.53.2 (2026), the current latest release:

• scripts/vendor.sh: downloads 2026/sqlite-amalgamation-3530200.zip
• Makefile: SQLITE_WASM_VERSION=3530200, SQLITE_WASM_YEAR=2026

tests/minimum/ is intentionally left at 3.31.1 since it exists to verify the minimum supported SQLite version. All SQLITE_VERSION_NUMBER gates in the source are minimum-version checks (3.38/3.44) already satisfied by the previous vendor, so no behavior changes.

Validation

• make loadable and make static build cleanly against the 3.53.2 vendor.

• Full Python suite passes: 478 passed, 132 skipped (feature-gated), 204 snapshots passed.

• WASM verified end-to-end with emcc: SQLite 3.49+ switched its build to autosetup, but everything make wasm relies on still works (./configure --enable-all, make sqlite3.c, the jswasm/sqlite3.mjs / jswasm/sqlite3.wasm targets, and the sqlite3_wasm_extra_init.c= override). A node smoke test against the resulting build returns correct vec0 KNN results:

  sqlite_version: 3.53.2
  vec_version: v0.1.10-alpha.4
  knn: [{"rowid":1,"distance":1},{"rowid":2,"distance":3.873}]
  

One note for local (non-emsdk) wasm builds: 3.53's ext/wasm requires a config.make that the SQLite configure script only generates when it detects an emsdk install (EMSDK env var / --with-emsdk). The release CI workflow uses setup-emsdk, which provides that, so make wasm works there unchanged.

What's new between 3.45.3 and 3.53.2

Full release history: https://sqlite.org/changes.html

A few additions in this range are directly useful to sqlite-vec (none are used by this PR; they would need SQLITE_VERSION_NUMBER / sqlite3_libversion_number() guards like the existing 3.38/3.44 gates, since the minimum supported SQLite remains 3.31.1):

• SQLITE_PREPARE_FROM_DDL (3.53.0): new sqlite3_prepare_v3() flag that "permits virtual table implementations to safely prepare SQL statements that are derived from the database schema". vec0 prepares many statements built from schema-derived shadow table names, so this is a natural hardening fit.
• sqlite3_set_errmsg() (3.51.0): API added specifically "for use by extensions" to set error messages.
• Virtual table DISTINCT optimization (3.53.0): vtabs can now optimize DISTINCT when the result set does not exactly match the ORDER BY clause (relevant to xBestIndex).
• sqlite3_str_truncate() / sqlite3_str_free() (3.53.0): small additions to the sqlite3_str API that sqlite-vec already uses for SQL construction.
• SQLITE_PREPARE_DONT_LOG (3.48.0): suppresses error-log noise when using prepare to test-compile SQL.
• 64-bit WASM support (3.51.0): the wasm build now also produces 64-bit variants; the canonical 32-bit builds that make wasm consumes are unchanged.

One behavior change worth knowing about: as of 3.53.0, floating-point-to-text conversion rounds to 17 significant digits by default instead of 15 (configurable via SQLITE_DBCONFIG_FP_DIGITS). This only affects SQLite's own float rendering, and the full test suite (including 204 snapshots) passes against 3.53.2.