ci: enable long-running RETRY conformance tests in nightly contract tests (#212)

**Requirements**

- [x] I have followed the repository's [pull request submission
guidelines](../blob/main/CONTRIBUTING.md#submitting-pull-requests)
- [ ] I have added test coverage for new or changed functionality — n/a,
CI configuration only
- [ ] I have validated my changes against all supported platform
versions — n/a, the nightly runs a single JDK, unchanged

**Related issues**

SDK-3007

**Describe the solution you've provided**

The nightly contract test job has been passing
`-enable-long-running-tests` to the **v3** harness step only. The
harness's long-running RETRY-conformance tests live on the **v2** line
(released in harness `v2.41.0`), so every one of them has been skipping
every night. From the 2026-09-03 nightly log:

```
SKIPPED: streaming/retry behavior/retry after unexpected HTTP error on initial connect (use -enable-long-running-tests to run)
SKIPPED: streaming/retry behavior/retry after unexpected HTTP error on reconnect (use -enable-long-running-tests to run)
SKIPPED: streaming/retry behavior/enters extended-regime backoff after unexpected HTTP error (use -enable-long-running-tests to run)
SKIPPED: streaming/retry behavior/does not permanently stop under sustained unexpected HTTP errors (use -enable-long-running-tests to run)
SKIPPED: streaming/retry behavior/returns to normal-regime backoff after healthy operation (use -enable-long-running-tests to run)
SKIPPED: polling/retry behavior (use -enable-long-running-tests to run)
```

The test service has declared `retry-conformance-fdv1-streaming` and
`retry-conformance-fdv1-polling` since #200, so these tests were ready
to run — they simply were not being asked to.

Changes:

- **v2 step gets `-enable-long-running-tests`.** This is the substantive
change; everything else supports it.
- **`timeout-minutes: 120`.** The job goes from ~11 min to an estimated
~60–90 min, and the 6-hour default is too permissive for a suite whose
failure mode is waiting.
- **`-junit` on both harness steps, at distinct paths,** plus `if:
always()` artifact uploads of the results and the test service log.
Triaging an hour-long run from raw step logs is impractical.
- **New "Create JUnit output directory" step.** The harness writes its
JUnit file with `os.WriteFile` and does not create parent directories; a
write error aborts the run, so `-junit` requires the directory to exist
first.
- **Notify on any non-clean pass** rather than only `failure`, with the
actual result included in the message, so a timeout or cancellation is
not silently swallowed.

On the history here: the flag originally applied to both harness
versions (#136) and was narrowed to v3-only the next day (#139). That
was correct at the time — the v2 long-running tests did not exist yet.
#164 faithfully preserved the narrowing when migrating to the shared
action. This restores v2 coverage now that there is something there to
run.

**Describe alternatives you've considered**

- **Splitting the long-running tests into a separate job,** so a timing
flake cannot mask the fast suite. Not done: it duplicates build and
service startup, and the fast suite costs about a minute inside the slow
job. Worth revisiting if the first couple of weeks show flakiness.
- **A `concurrency` group** to stop a manual dispatch overlapping the
scheduled run. Rejected: GitHub-hosted jobs each get their own ephemeral
VM, so concurrent runs share no port and no state. A group would only
queue a dispatch behind an in-flight ~90-minute run, or silently cancel
a superseded pending run — which would obstruct the dispatch-based
validation this change relies on.
- **`run_tests: 'false'` on the shared CI action** to skip duplicate
unit tests. Rejected after measuring: `gradlew build` already runs them
(~3.5 min), and the separate Run Tests step is `:test UP-TO-DATE` in one
second. It would have saved a second, not the ten minutes I initially
assumed.

**Additional context**

- **Expect a much longer nightly.** These tests wait on real RETRY
backoff timing (a 5-minute extended-regime delay with up to 50% jitter)
and the harness runs tests sequentially, so the runtime is almost
entirely sleeping. Failures are *slower* than passes: a regression that
stops retrying makes each scenario burn its full timeout instead of
returning early.
- **Validation before merge:** dispatch this workflow against this
branch and confirm zero `use -enable-long-running-tests to run` lines —
`gh workflow run nightly-contract-tests.yml --ref
ta/SDK-3007/nightly-long-running-tests`. That run takes about an hour.
- The Slack notification wiring is unchanged in shape. Note the webhook
has not been functional, so failures are currently discoverable only
from the Actions tab; fixing that is tracked separately and deliberately
out of scope here.
- The v3 harness step stays pinned at `v3.0.0-alpha.6`; bumping it would
pull in new FDv2 tests and require re-validating the FDv2 suppressions.
- `actions/checkout@v3` in this workflow is flagged by actionlint as too
old. Pre-existing on `main` and left alone here.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Overview**
> The nightly contract test job now runs **v2** harness long-running
RETRY conformance tests by adding `-enable-long-running-tests` to the v2
step (they were previously skipped while only v3 had the flag).
> 
> To support ~hour-long runs, the main job gets a **120-minute
timeout**, JUnit output via `-junit` on both v2 and v3 steps (with a
**`junit/` directory** created first), and **`if: always()` artifact
uploads** for JUnit XML and the contract test service log.
> 
> Slack notification now fires on **any non-success** outcome
(timeout/cancel included) and reports the actual job result instead of
only hard failures.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
bd06463. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: tanderson-ld

.github/workflows/nightly-contract-tests.yml

@@ -18,6 +18,11 @@ on:
 jobs:
   nightly-contract-tests:
     runs-on: ubuntu-latest
+    # The long-running tests wait on real RETRY backoff timing, so this job runs
+    # roughly an hour. A regression that stops retrying makes every scenario burn
+    # its full timeout instead of returning early, so leave headroom -- while
+    # staying well under the 6-hour default that would otherwise apply.
+    timeout-minutes: 120
     steps:
       - uses: actions/checkout@v3
         with:
@@ -37,6 +42,10 @@ jobs:
         shell: bash
         run: make start-contract-test-service-bg -C lib/sdk/server
 
+      - name: Create JUnit output directory
+        shell: bash
+        run: mkdir -p junit
+
       - name: Contract Tests (v2)
         uses: launchdarkly/gh-actions/actions/contract-tests@contract-tests-v1
         with:
@@ -45,7 +54,7 @@ jobs:
           debug_logging: 'true'
           stop_service: 'false'
           enable_persistence_tests: 'false'
-          extra_params: '-skip-from=lib/sdk/server/contract-tests/test-suppressions.txt'
+          extra_params: '-skip-from=lib/sdk/server/contract-tests/test-suppressions.txt -enable-long-running-tests -junit junit/contract-tests-v2.xml'
 
       - name: Contract Tests v3 (with long-running tests)
         uses: launchdarkly/gh-actions/actions/contract-tests@contract-tests-v1
@@ -56,11 +65,29 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
           debug_logging: 'true'
           enable_persistence_tests: 'false'
-          extra_params: '-skip-from=lib/sdk/server/contract-tests/test-suppressions-fdv2.txt -enable-long-running-tests'
+          extra_params: '-skip-from=lib/sdk/server/contract-tests/test-suppressions-fdv2.txt -enable-long-running-tests -junit junit/contract-tests-v3.xml'
+
+      - name: Upload contract test results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: contract-test-results
+          path: junit/
+          if-no-files-found: warn
+
+      - name: Upload contract test service log
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: contract-test-service-log
+          path: /tmp/sdk-test-service.log
+          if-no-files-found: warn
 
   notify-slack-on-failure:
     runs-on: ubuntu-latest
-    if: ${{ always() && needs.nightly-contract-tests.result == 'failure' }}
+    # Any outcome that is not a clean pass, not just 'failure' -- this also
+    # covers a timeout or an infrastructure cancellation.
+    if: ${{ always() && needs.nightly-contract-tests.result != 'success' }}
     needs:
       - nightly-contract-tests
     steps:
@@ -76,7 +103,7 @@ jobs:
                   "type": "section",
                   "text": {
                     "type": "mrkdwn",
-                    "text": ":warning: *Nightly Contract Tests Failed* :warning:\nThe nightly contract tests (with long-running tests enabled) failed on `${{ github.ref_name }}`."
+                    "text": ":warning: *Nightly Contract Tests Did Not Pass* :warning:\nThe nightly contract tests (with long-running tests enabled) finished with result `${{ needs.nightly-contract-tests.result }}` on `${{ github.ref_name }}`."
                   },
                   "accessory": {
                     "type": "button",