Update CreatePortal to record closed_at timestamp

[KCarretto]

This change ensures that when a portal is closed via the CreatePortal gRPC method, the closed_at timestamp is correctly recorded in the database. The logic for this update was moved from the portal mux to the C2 API layer to better synchronize with the closure signal sent to subscribers. An integration test was updated to verify this behavior.

---

PR created automatically by Jules for task 3624297369847578282 started by @KCarretto

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.

[github-actions]

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
2946	2945	1	0	0	0	1ms

Previous Results

Build 🏗️	Result 🧪	Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
#2050	❌	2946	2945	1	0	0	0	493368h 7m

Insights

Average Tests per Run	Total Flaky Tests	Total Failed	Slowest Test (p95)
2946	0	1	4m 37s

Fail Rate

Fail Rate	0.03%

Test 📝	Results 📊	Passed ✅	Failed ❌	Fail Rate (%) 📈
TestMux_CreatePortal	1	0	1	100.00    ↑100.00

Failed Tests

Failed Tests

❌ TestMux_CreatePortal === RUN TestMux_CreatePortal 2026/04/14 00:07:01 INFO Starting receive loop topic=PORTAL_IN_1 2026/04/14 00:07:01 INFO New subscription topic=PORTAL_IN_1 2026/04/14 00:07:01 INFO Receive loop exited topic=PORTAL_IN_1 mux_test.go:135: Error Trace: /home/runner/work/realm/realm/tavern/internal/portals/mux/mux_test.go:135 Error: Should be false Test: TestMux_CreatePortal 2026/04/14 00:07:01 INFO Subscription canceled topic=PORTAL_IN_1 --- FAIL: TestMux_CreatePortal (0.02s) Trace: No trace available

Test Changes

0 test added, 0 removed

Slowest Tests

Test 📝	Results 📊	Duration (avg) ⏱️	Duration (p95) ⏱️
eldritch-libfile: std::list_recent_impl::tests::test_list_recent_default_args	3	3m 20s	4m 37s
eldritch-libfile: std::list_recent_impl::tests::test_list_recent_default_args	3	3m 20s	4m 37s
eldritch-libfile: std::list_recent_impl::tests::test_list_recent_default_args	3	3m 20s	4m 37s
TestDockerExecutor_Build_ContextCancellation	1	6.2s	6.2s
eldritch-libsys: std::dll_inject_impl::tests::test_dll_inject_simple	1	5.2s	5.2s
TestInteractiveShell	1	5.1s	5.1s
TestOtherStreamOutput	1	5.0s	5.0s
TestDockerExecutor_Build_SimpleEcho	1	3.9s	3.9s
imix::bin/imix: tests::task_tests::test_task_eprint_behavior	3	3.0s	3.1s
imix::bin/imix: tests::task_tests::test_task_eprint_behavior	3	3.0s	3.1s

_{🍂 No flaky tests in this run.}

Github Test Reporter by CTRF 💚