feat: add native Oracle transactions

[ryanrasti]

Refactor runInSingleConnection to runInTransaction -- drivers manage transactions themselves.

[Copilot]

Pull request overview

This PR refactors the driver transaction contract to a single runInTransaction(options, cb) entrypoint and adds native transaction support for the Oracle driver (including integration tests), while updating Connection.transaction() to delegate transaction boundaries to drivers.

Changes:

• Replace runInSingleConnection / optional native transaction hooks with required Driver.runInTransaction(opts, cb) and shared transaction helpers (runTransaction, runSqlTransaction).
• Implement runInTransaction across pg/pglite/sqlite/do/oracle drivers and route Connection.transaction() through the driver-owned transaction protocol.
• Add/adjust tests for rollback behavior (DO sqlite live test) and add Oracle transaction coverage (opt-in via ORACLE_URL).

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/test-helpers.ts	Updates compile-only driver stub to satisfy the new runInTransaction contract.
src/live/sqlite/db-live.test.ts	Exercises DO driver transaction behavior (commit + rollback) under live queries.
src/drivers/types.ts	Introduces TransactionOptions/TransactionIsolation and makes runInTransaction required.
src/drivers/transaction.ts	Adds shared transaction state machine + SQL begin/commit/rollback helper.
src/drivers/transaction.test.ts	Adds unit tests for the new transaction helpers.
src/drivers/sqlite.ts	Implements SQL-based transactions via runSqlTransaction.
src/drivers/pglite.ts	Implements SQL-based transactions with optional isolation handling.
src/drivers/pg.ts	Implements SQL-based transactions with pooled client pinning and optional isolation.
src/drivers/oracle.ts	Adds native Oracle transaction pinning + commit/rollback using oracledb APIs.
src/drivers/oracle.test.ts	Updates driver stub shape for the new runInTransaction API.
src/drivers/oracle-transaction.test.ts	Adds opt-in Oracle transaction integration tests (commit/rollback/nesting).
src/drivers/do.ts	Updates DO SqlStorage driver to the new runInTransaction(opts, cb(execute)) shape.
src/database.ts	Delegates transaction lifecycle to drivers and keeps nested isolation rules.
docs/ARCHITECTURE.md	Updates architecture docs to reflect the new driver transaction model and Oracle support.

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