fix(webapp): treat FAILED buffered runs as terminal in the run-header synth

`buildSyntheticRunHeader` only checked for `CANCELED` when mapping
`SyntheticRun.status` to the run-header's `status` / `isFinished`
fields. `SyntheticRun.status` can also be `"FAILED"` (set by
`readFallback.server.ts` when the buffer entry's status is FAILED —
e.g. after the drainer's terminal-failure path), so a FAILED buffered
run showed in the page header as `PENDING` + `isFinished: false`,
which left the Cancel button visible for an already-failed run.

Add a parallel `isFailed` branch (mapping to `SYSTEM_FAILURE`, matching
`buildSyntheticSpanRun`'s same-shape decision for the right-side panel)
and OR it into `isFinished`. Symmetric across the header + span panel
so admins no longer see "Pending" + "FAILED" simultaneously on the
same run.

Devin follow-up on PR #3757.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: d-cs

apps/webapp/app/v3/mollifier/syntheticRunHeader.server.ts

@@ -5,13 +5,19 @@ import type { SyntheticRun } from "./readFallback.server";
 // shape matches `RunPresenter.getRun`'s `runData` — keep this in sync
 // when fields are added there.
 //
-// CANCELED state is reflected back from `SyntheticRun.cancelledAt` /
-// `status` so that after a buffered-cancel the NavBar shows the run as
-// CANCELED + isFinished:true (which collapses the Cancel button) before
-// the drainer materialises the PG row. This mirrors what
-// `buildSyntheticSpanRun` does for the right-side details panel — the
-// SyntheticRun.cancelledAt contract comment in readFallback.server.ts
-// names this exact UI surface.
+// CANCELED and FAILED state is reflected back from
+// `SyntheticRun.cancelledAt` / `status` so terminal buffered runs show
+// the correct status in the NavBar + isFinished:true (which collapses
+// the Cancel button on the page header) before the drainer materialises
+// the PG row. This mirrors what `buildSyntheticSpanRun` does for the
+// right-side details panel — the SyntheticRun.cancelledAt contract
+// comment in readFallback.server.ts names this exact UI surface.
+//
+// FAILED status maps to `SYSTEM_FAILURE` to match the drainer's
+// non-retryable terminal path, which is what `buildSyntheticSpanRun`
+// uses too. Symmetric across the header + span-detail panel so an
+// admin doesn't see "Pending" + "FAILED" simultaneously on the same
+// run.
 export function buildSyntheticRunHeader(args: {
   run: SyntheticRun;
   environment: {
@@ -23,15 +29,20 @@ export function buildSyntheticRunHeader(args: {
 }) {
   const { run, environment } = args;
   const isCancelled = run.status === "CANCELED";
+  const isFailed = run.status === "FAILED";
 
   return {
     id: run.friendlyId,
     number: 1,
     friendlyId: run.friendlyId,
     traceId: run.traceId ?? "",
     spanId: run.spanId ?? "",
-    status: isCancelled ? ("CANCELED" as const) : ("PENDING" as const),
-    isFinished: isCancelled,
+    status: isCancelled
+      ? ("CANCELED" as const)
+      : isFailed
+      ? ("SYSTEM_FAILURE" as const)
+      : ("PENDING" as const),
+    isFinished: isCancelled || isFailed,
     startedAt: null,
     completedAt: run.cancelledAt ?? null,
     logsDeletedAt: null,