feat(FN-4219): complete Steps 5-7 — docs, changeset, and verification fixes

Fusion-Task-Id: FN-4219
Fusion-Task-Lineage: 8d9a9ba6-6729-4376-b935-549e28a7fa35

packages/engine/src/__tests__/experiment-git-policy.test.ts

@@ -22,8 +22,7 @@ const baseSession: ExperimentSession = {
   currentSegment: 1,
   maxIterations: 10,
   tags: [],
-  bestRunId: null,
-  baselineCommit: null,
+  bestRunId: undefined,
   keptRunIds: [],
   createdAt: new Date().toISOString(),
   updatedAt: new Date().toISOString(),
@@ -33,8 +32,9 @@ const baseRunRecord: ExperimentSessionRecord = {
   id: "EXPR-001",
   sessionId: "EXP-001",
   segment: 1,
+  seq: 1,
   type: "run",
-  payload: { status: "keep", secondaryMetrics: [] },
+  payload: { status: "keep", primaryMetric: 0.91, secondaryMetrics: [] },
   createdAt: new Date().toISOString(),
 };
 

packages/engine/src/experiment/benchmark-runner.ts

@@ -58,8 +58,6 @@ export async function runBenchmark(
     let truncatedTempFile: string | undefined;
     let progressStdoutChunk = "";
     let progressStderrChunk = "";
-    let finished = false;
-
     const emitProgress = () => {
       if (!opts.onProgress) {
         progressStdoutChunk = "";
@@ -121,7 +119,6 @@ export async function runBenchmark(
     child.on("error", (error) => {
       cleanup();
       if ((error as NodeJS.ErrnoException).name === "AbortError") {
-        finished = true;
         resolve({
           exitCode: 1,
           stdout: truncated ? (stdoutFull + stdoutTail).slice(-STDOUT_TAIL_BYTES) : stdoutFull,
@@ -157,7 +154,6 @@ export async function runBenchmark(
       const effectiveStdout = truncated
         ? (stdoutFull + stdoutTail).slice(-STDOUT_TAIL_BYTES)
         : stdoutFull;
-      finished = true;
       resolve({
         exitCode: code ?? (signal ? 1 : 0),
         stdout: effectiveStdout,