test: add cross-node invariant checks

[shuowang12]

Description

Describe the changes or additions included in this PR.

Test plan

How did you test the new or updated feature?

---

Release notes

Check each box that your changes affect. If none of the boxes relate to your changes, release notes aren't required.
For each box you select, include information after the relevant heading that describes the impact of your changes that
a user might notice and any actions they must take to implement updates. (Add release notes after the colon for each item)

• Storage node:
• Aggregator:
• Publisher:
• CLI:

[wbbradley]

Claude says: Soft-invariant streak counters are not reset on skipped rounds in Antithesis observer. When a node
is unreachable the round is skipped via continue, but event_source_streak and fully_stored_streak retain their previous values. This means non-consecutive violations separated by skipped rounds still accumulate toward the patience threshold, causing false-positive crashes in the exact fault-injection environment (Antithesis) where the script runs. Fix: reset both streak counters to 0 inside the all_ok=false branch before continue. (docker/walrus-antithesis/build-test-config-image/files/run-observer.sh:170-185)

[shuowang12]

Claude says: Soft-invariant streak counters are not reset on skipped rounds in Antithesis observer. When a node is unreachable the round is skipped via continue, but event_source_streak and fully_stored_streak retain their previous values. This means non-consecutive violations separated by skipped rounds still accumulate toward the patience threshold, causing false-positive crashes in the exact fault-injection environment (Antithesis) where the script runs. Fix: reset both streak counters to 0 inside the all_ok=false branch before continue. (docker/walrus-antithesis/build-test-config-image/files/run-observer.sh:170-185)

Thanks for the notes. I am still trying to figure out how to run the Antithesis tests against a branch/PR and thus created this draft PR. Will address the issue later.