fix(plugins): collect quarantined batches instead of leaving them on disk forever

Review finding. _sweep_debris globbed only *.partial. The *.corrupt files this
PR writes when a batch cannot be decoded are matched by no glob in the module, so
they accumulated for the life of the install.

Collected on the expiry window rather than the stale window, deliberately: a
quarantined batch is the only remaining evidence of events that could not be
delivered, so someone chasing a report of missing telemetry has to be able to
find a recent one. Debris keeps the short window; it carries nothing.

One test, asserting both halves: a recent quarantine survives and an expired one
does not.

Claude-Session: https://claude.ai/code/session_01C7tEmH86HAr7GoAAKCEHZb

integrations/agent-plugin-core/tests/test_spool_delivery.py

@@ -409,3 +409,24 @@ def test_partial_files_are_swept(telemetry):
 
     telemetry.flush()
     assert not debris.exists()
+
+
+def test_quarantined_batches_are_eventually_collected(telemetry):
+    """Nothing re-globs .corrupt, so without a sweep they live on disk forever.
+
+    Kept much longer than .partial debris on purpose: a quarantined batch is the
+    only remaining evidence of events that could not be delivered.
+    """
+    directory = telemetry.memory_core.data_dir()
+    directory.mkdir(parents=True, exist_ok=True)
+    fresh = directory / "telemetry-1-aaaaaaaa-a0.corrupt"
+    old = directory / "telemetry-2-bbbbbbbb-a0.corrupt"
+    for path in (fresh, old):
+        path.write_text("torn", encoding="utf-8")
+    expired = time.time() - (telemetry.CLAIM_EXPIRY_SECONDS + 60)
+    os.utime(old, (expired, expired))
+
+    telemetry._sweep_debris(directory)
+
+    assert fresh.exists(), "a recent quarantine was discarded before anyone could look at it"
+    assert not old.exists(), "an expired quarantine was left on disk forever"