Summary

Closes #4249

Adds session.Events.ProjectLatest<T>(id) — a new API that returns the projected aggregate state including any events appended in the current session but not yet committed via SaveChangesAsync().

Before (forced flush + re-read):

session.Events.StartStream<Report>(id, new ReportCreated("Q1"));
await session.SaveChangesAsync(ct);  // forced flush
var report = await session.Events.FetchLatest<Report>(id, ct);  // re-read

After (project locally):

session.Events.StartStream<Report>(id, new ReportCreated("Q1"));
var report = await session.Events.ProjectLatest<Report>(id, ct);
// SaveChangesAsync happens later

Behavior by projection lifecycle:

• Live: fetches committed events from DB, builds aggregate, then applies pending events on top
• Inline: loads pre-projected document, applies pending events, stores updated document in session for persistence on SaveChangesAsync()
• Async: same as inline
• Natural key: falls back to FetchLatest (pending events use stream IDs, not natural keys)

Test plan

• Live projection: pending events from StartStream are included
• Inline projection: pending events are included
• Inline projection: updated document is stored and persisted on SaveChangesAsync
• No pending events: behaves like FetchLatest
• Live projection: committed + pending events combined
• Nonexistent stream returns null

🤖 Generated with Claude Code