fix(plugins): stop the new spool tests depending on ambient state

CI runs agent-plugin-core/tests and claude-code-plugin/tests in one pytest
process. Two things only show up in that combined run, so the suites passed
locally and failed on every push.

claude-code-plugin/tests/conftest.py sets MEM0_TELEMETRY=false at import, which
is process-wide. record() then returns early and every assertion in
test_spool_delivery.py saw an empty spool — nine failures, all reported as
"recorded nothing" rather than as a disabled feature. The fixture now pins
MEM0_TELEMETRY rather than trusting whatever collected first.

The fixture also dropped telemetry/memory_core/_harness_id from sys.modules on
teardown. That conftest imports memory_core once at collection and calls
configure_harness() on it, so a later re-import got a fresh module with default
harness config and test_memory_core failed depending on collection order. The
fixture now saves and restores those entries instead of deleting them.

Verified with CI's exact command rather than the narrower path I had been
running: 266 passed, 8 skipped.

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

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

@@ -25,15 +25,32 @@ pytestmark = pytest.mark.skipif(not HOST_CORE.exists(), reason="claude-code-plug
 
 @pytest.fixture()
 def telemetry(tmp_path, monkeypatch):
+    # CI runs this directory and claude-code-plugin/tests in ONE pytest process,
+    # and that suite's conftest sets MEM0_TELEMETRY=false at import, process-wide.
+    # Without this the whole file silently no-ops: record() returns early and
+    # every assertion sees an empty spool. Do not rely on ambient env.
+    monkeypatch.setenv("MEM0_TELEMETRY", "true")
     monkeypatch.setenv("MEM0_CODE_DATA_DIR", str(tmp_path / "data"))
     monkeypatch.syspath_prepend(str(HOST_CORE))
-    for name in ("telemetry", "memory_core", "_harness_id"):
+
+    # Save and RESTORE rather than delete. claude-code-plugin/tests/conftest.py
+    # imports memory_core once at collection and calls configure_harness() on it;
+    # dropping the module left a later re-import with default harness config, so
+    # tests in that suite failed depending on collection order.
+    names = ("telemetry", "memory_core", "_harness_id")
+    saved = {name: sys.modules.get(name) for name in names}
+    for name in names:
         sys.modules.pop(name, None)
+
     module = importlib.import_module("telemetry")
     monkeypatch.setattr(module, "resolve_distinct_id", lambda: ("tester@example.com", ""))
-    yield module
-    for name in ("telemetry", "memory_core", "_harness_id"):
-        sys.modules.pop(name, None)
+    try:
+        yield module
+    finally:
+        for name in names:
+            sys.modules.pop(name, None)
+            if saved[name] is not None:
+                sys.modules[name] = saved[name]
 
 
 def _delivered(payloads):