fix: preserve primary detail hash across frontmatter retries

When the agent's first run output fails frontmatter extraction, the
retry loop (via options.continue) would replace agentResult entirely,
causing the 1-turn continuation detail to overwrite the original
multi-turn detail containing all tool-call history.

Now we capture primaryDetailHash from the first run and always use it
for the persisted StepNode, regardless of how many retries occur.

Fixes #439

packages/workflow-agent-kit/src/run.ts

@@ -121,6 +121,11 @@ export function createAgent(options: AgentOptions): () => Promise<void> {
 
     let agentResult = await runWithMessage("agent run failed", () => options.run(ctx));
 
+    // Preserve the primary detail from the first run — it contains the full
+    // tool-call turn history.  Continuation retries only fix frontmatter
+    // formatting and their 1-turn detail is not meaningful.
+    const primaryDetailHash = agentResult.detailHash;
+
     // Try to extract frontmatter; retry via continue if it fails
     let outputHash = await tryExtractOutput(agentResult.output, roleDef.frontmatter, ctx);
 
@@ -147,7 +152,7 @@ export function createAgent(options: AgentOptions): () => Promise<void> {
     const stepHash = await persistStep({
       ctx,
       outputHash,
-      detailHash: agentResult.detailHash,
+      detailHash: primaryDetailHash,
       agentName: agentLabel(options.name),
     });