refactor(kernel-store): one copy of the savepoint and transaction methods

[sirtimid]

The Node and wasm drivers carried the same six transaction and savepoint methods, beginIfNeeded, commitIfNeeded, rollbackIfNeeded, createSavepoint, rollbackSavepoint and releaseSavepoint, differing only in how a prepared statement runs.

They move into the internal sqlite/transactions.ts, built by makeTransactionMethods({ db, begin, commit, abort }), and each driver injects its three statement runners.

• The TransactionalDatabase docstring records where _spStack and SQLite's savepoint stack disagree, as Extract the duplicated sqlite savepoint methods into one module #1013 asks, and why that is safe: no name is opened twice on the stack.
• One behaviour change, wasm only: runStatement resets in a finally. A COMMIT that failed with the transaction left open stayed busy, so the connection kept a read lock past the ROLLBACK that followed.
• The moved rollbackSavepoint comment, and the fix(ocap-kernel): report a dead run loop instead of a healthy kernel #1005 changelog entry, no longer claim a failed rollback discards only what it was abandoning.

Testing

• The savepoint tests duplicated across both driver suites are now one suite, transactions.test.ts, against a fake database. beginIfNeeded, commitIfNeeded and rollbackIfNeeded get direct tests there, and a repeated name resolves to its newest savepoint.
• Each driver keeps one test that it runs its own prepared statements.
• A real-SQLite test fails a COMMIT on a deferred foreign key, rolls back, and drops a table; without the finally the drop hits SQLITE_LOCKED.
• vatStore.updateKVData's begin and commit assertions check the BEGIN and COMMIT statements; they were checking the kv statement.

Closes #1013

🤖 Generated with Claude Code

---

Note

Medium Risk
Changes shared persistence transaction/savepoint behavior for both drivers; the wasm COMMIT-reset fix alters lock lifecycle after errors, though behavior is heavily tested.

Overview
Unifies SQLite transaction and savepoint handling across the Node (better-sqlite3) and wasm drivers by moving beginIfNeeded, commitIfNeeded, rollbackIfNeeded, and the three savepoint APIs into shared makeTransactionMethods in sqlite/transactions.ts. Each driver only supplies how it runs its prepared BEGIN/COMMIT/ROLLBACK statements.

The wasm driver now runs those statements (and clear) through a runStatement helper that always resets after step(), fixing a case where a failed COMMIT left the statement busy and held a read lock so DROP TABLE / VACUUM failed until the next commit (#1092).

Tests: duplicated savepoint suites in nodejs.test.ts and wasm.test.ts are replaced by transactions.test.ts against a fake DB; each driver keeps one test that its own prepared statements are invoked. Integration coverage adds the post-failed-COMMIT DROP TABLE scenario in wasm.transactions.test.ts. Changelog wording for failed rollbackSavepoint is clarified.

^{Reviewed by Cursor Bugbot for commit be53378. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	73.58% ⬇️ -0.02%	10184 / 13840
🔵	Statements	73.34% ⬇️ -0.02%	10322 / 14074
🔵	Functions	73.57% ⬆️ +0.03%	2389 / 3247
🔵	Branches	68.42% ⬇️ -0.02%	4240 / 6197

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
packages/kernel-store/src/sqlite/nodejs.ts	98.52% ⬇️ -0.48%	91.66% ⬇️ -4.76%	100% 🟰 ±0%	98.52% ⬇️ -0.48%	76
packages/kernel-store/src/sqlite/transactions.ts	100%	100%	100%	100%
packages/kernel-store/src/sqlite/wasm.ts	100% ⬆️ +2.02%	96.15% ⬆️ +6.68%	100% 🟰 ±0%	100% ⬆️ +2.03%

Generated in workflow #5236 for commit be53378 by the Vitest Coverage Report Action