Build without the optional mysql2 and sqlite3 drivers

[GermanBluefox]

The DB drivers are optionalDependencies and are import()ed lazily, so a missing one is meant to degrade to a log message. The build was stricter than the runtime: import type { Database } from 'sqlite3' makes TypeScript resolve the package while type checking, and so does import('sqlite3') — even though that specifier is only ever evaluated at runtime. Both fail with TS2307 when the driver is absent.

Not hypothetical: adapter-tests-sqlite (24.x, macos-latest) failed exactly this way on #578. npm skipped 38 optional packages on that runner (sqlite3, cpu-features, diskusage, unix-dgram and their trees) with nothing but a warning — 631 packages installed instead of 669 — and npm run build:ts then died:

src/lib/sqlite3-client.ts(5,31): error TS2307: Cannot find module 'sqlite3' or its corresponding type declarations.
src/lib/sqlite3-client.ts(16,25): error TS2307: Cannot find module 'sqlite3' or its corresponding type declarations.

What breaks, measured

Removing one driver at a time from node_modules and running tsc:

driver removed	result
sqlite3	2 errors (sqlite3-client.ts:5, :16)
mysql2	3 errors (connection-options.ts:1, mysql-client.ts:5, :13)
mssql	ok
pg	ok

Only the two drivers that ship their types inside the package break. pg and mssql are covered by @types/pg and @types/mssql, which are regular devDependencies and therefore always installed.

The change

src/lib/optional-drivers.ts declares the sliver of mysql2 and sqlite3 this adapter actually touches — Database.close/.all, the two new Database(...) overloads, Connection.end, and the connection options we set — plus importDriver(), which routes the specifier through a string so the type checker cannot resolve it either.

The emitted code is unchanged in substance:

void (0, optional_drivers_1.importDriver)('sqlite3').then(sqlite3 => { ... })
...
function importDriver(name) { return import(name); }

Verification

• tsc succeeds with all four drivers absent, and with each one absent individually.
• Runtime unchanged: opening an in-memory SQLite database, running SELECT 42, sqlite_version() and closing it all still work.
• The degradation path still holds — with sqlite3 removed, openConnection reports Node.js DB driver "sqlite3" could not be loaded: ERR_MODULE_NOT_FOUND instead of crashing.
• check:ts and lint (root and src-admin) clean, 195 unit tests passing.

Verified in a checkout outside C:\pWork, because a stray package.json/node_modules there makes every driver resolve from an ancestor directory and hides exactly this class of problem.

🤖 Generated with Claude Code