fix(test-runner): bun's headerless failure recap can't invent a phantom failing file

Round-3 CI showed the remaining half of the recap bug: bun prints
'N tests failed:' then re-prints every (fail) line with NO file
headers, so they attributed to the stale currentFile — an innocent
file (test/uninstall.test.ts) was charged with another file's 5
failures. The recap marker now ends attribution (currentFile=null,
chunk closed) and recap re-prints of already-recorded test names
dedupe; a recap-only failure the main run never attributed still
records, unattributed, as belt and braces.

scripts/test-free-shards.ts

@@ -587,6 +587,7 @@ export class FreeRunReporter {
   private readonly failures: FreeRunFailure[] = [];
   private readonly crashed = new Set<string>();
   private currentFile: string | null = null;
+  private inRecap = false;
   private testsRan: number | null = null;
   private filesRan: number | null = null;
   private sawSummary = false;
@@ -646,6 +647,16 @@ export class FreeRunReporter {
     const line = stripAnsiLine(rawLine).replace(/^::group::/, '');
     let visible = false;
 
+    // Bun's terminal recap ("N tests failed:") re-prints every (fail) line
+    // WITHOUT re-printing file headers. Attributing those to the stale
+    // currentFile invented a phantom failing file on the first Linux run
+    // (5 real failures reported as 10 across 2 files, one innocent).
+    if (/^\d+ tests? failed:$/.test(line)) {
+      this.inRecap = true;
+      if (this.currentFile) this.progressFor(this.currentFile).ended = true;
+      this.currentFile = null;
+    }
+
     const header = FILE_HEADER_RE.exec(line);
     if (header) {
       const file = this.canonicalize(header[1]);
@@ -661,8 +672,12 @@ export class FreeRunReporter {
       const final = fail || retry ? null : CRASH_FINAL_RE.exec(line);
       if (fail) {
         visible = true;
+        // In the recap, a (fail) line only records a failure the main run
+        // somehow never attributed (belt and braces); known names dedupe.
+        const recapDuplicate = this.inRecap
+          && this.failures.some((f) => f.testName === fail[1]);
         const key = `${this.currentFile ?? ''}\u0000${fail[1]}`;
-        if (!this.failureKeys.has(key)) {
+        if (!recapDuplicate && !this.failureKeys.has(key)) {
           this.failureKeys.add(key);
           this.failures.push({ file: this.currentFile, testName: fail[1] });
         }

test/test-free-shards.test.ts

@@ -505,6 +505,23 @@ describe('test-free-shards: GitHub Actions log-group attribution', () => {
     reporter.end();
     expect(reporter.report().failures).toEqual([{ file: 'test/b.test.ts', testName: 'planted' }]);
   });
+
+  test('headerless recap re-prints do not invent a phantom failing file', () => {
+    // Round-3 CI shape: bun's recap prints "N tests failed:" then the (fail)
+    // lines with NO file headers — the stale currentFile (an innocent file)
+    // was charged with the previous file's failures.
+    const reporter = new FreeRunReporter(['test/a.test.ts', 'test/b.test.ts']);
+    reporter.write('::group::test/a.test.ts:\n', 'stderr');
+    reporter.write(`${failLine('planted')}\n`, 'stderr');
+    reporter.write('::endgroup::\n', 'stderr');
+    reporter.write('::group::test/b.test.ts:\n', 'stderr');
+    reporter.write('(pass-ish output, no failures here)\n', 'stderr');
+    reporter.write('2 tests failed:\n', 'stderr');
+    reporter.write(`${failLine('planted')}\n`, 'stderr');
+    reporter.write(`${failLine('planted')}\n`, 'stderr');
+    reporter.end();
+    expect(reporter.report().failures).toEqual([{ file: 'test/a.test.ts', testName: 'planted' }]);
+  });
 });
 
 describe('test-free-shards: curated-list census pins', () => {