auth: add RevertFact method to recordingAPI test helper

recordingAPI did not implement the new CoreAPI.RevertFact method
added in a02e10f, causing a build failure in auth tests.

Also adds coverage.out to .gitignore.

.gitignore

@@ -27,3 +27,6 @@ deploy/db_key.env
 
 # opencode config (per-project, not for sharing)
 opencode.json
+
+# Test coverage output
+coverage.out

internal/auth/auth_test.go

@@ -379,6 +379,10 @@ func (r *recordingAPI) ListTools(_ context.Context, _ string) ([]ipc.Tool, error
 	return nil, nil
 }
 
+func (r *recordingAPI) RevertFact(_ context.Context, _ string) (int64, error) {
+	return 0, nil
+}
+
 // mustWriteFactParams — minimal WriteFactReq JSON with only the source field,
 // matching what ipc.dispatch hands to Server.Check (the raw params frame).
 func mustWriteFactParams(source string) []byte {