Test SQLite projection writes, asynchronous handlers, and failure cleanup

[nmummau]

Problem

SqliteProjector has no recorded line coverage in the October 5, 2026 .NET 10 coverage run. Existing SQLite event-store tests do not establish that registered projection handlers correctly build and execute commands or handle failures. You can view a test coverage report I generated here: index.html

Source: SqliteProjector.cs.

Proposed tests

• Define a small read-model projector and handle an event using a synchronous command-building handler. Query a real temporary SQLite database and assert the resulting row values.
• Repeat with an asynchronous handler whose command creation is controlled by a completion signal. Verify that handling waits for it and that no row is written before it is released.
• Project multiple events and verify the resulting read-model state, including parameterized values and event-context data used by the projection.
• Make a command-building handler fail and verify that the error reaches the caller without writing a row.
• Execute an invalid SQL command and verify error propagation and that a subsequent valid projection succeeds.
• Cancel handling while an asynchronous handler is waiting. Verify cancellation propagation and that the cancelled handler's command is not executed.

Acceptance criteria

• Both handler overloads are exercised through the projector's public event-handling entry point.
• Assertions inspect real database state, not only mocked command calls.
• Asynchronous completion, handler failure, SQL failure, and cancellation have observable assertions.
• Connections are released on successful and failed handling, and subsequent valid operations remain usable.
• Tests use isolated temporary databases and clean up their resources.
• Tests do not call task or disposal extensions directly and require no Docker containers.

Validation

Run the focused SQLite projection tests and the existing SQLite suite. Collect coverage for SqliteProjector; unrelated SQL Server and PostgreSQL suites are not required for this test-only change.

[linear]

EVE-258

[nmummau]

I’ve implemented this locally with regression tests. I’m waiting for a prerequisite PR 603 to merge so I can rebase and open a focused PR. I’ll link it here once it’s ready.