ci: verify every local-env validator reaches finality

[ozgb]

Overview

Recently, a PR was merged that broke finality for nodes 4 and 5 on local-env - but CI passed without issue.

This PR adds finality checks for all nodes on local env:

Add a verify-finality <network> ts-node command that polls
chain_getFinalizedHead on every validator's RPC and fails if any node
hasn't finalized within the timeout. Wire it into the local-environment
GitHub action between deploying the stack and running e2e tests.

GRANDPA needs 2/3 quorum; if any validator is stuck or panicking
finality stalls. Probing every node up-front surfaces that
deterministically rather than letting downstream tests time out further
along, and in particular catches regressions in the unified-storage
nodes (4 and 5) which currently don't have dedicated coverage.

Also extends check-health.sh with an optional -f|--finalized flag
for shell parity; default behaviour unchanged.

🗹 TODO before merging

• Ready

📌 Submission Checklist

• All commits are signed off (git commit -s) for the DCO
• Changes are backward-compatible (or flagged if breaking)
• Pull request description explains why the change is needed
• Self-reviewed the diff
• I have included a change file, or skipped for this reason: Internal testing change
• If the changes introduce a new feature, I have bumped the node minor version
• Update documentation (if relevant)
• Updated AGENTS.md if build commands, architecture, or workflows changed
• No new todos introduced

🧪 Testing Evidence

Please describe any additional testing aside from CI:

• Additional tests are provided (if possible)

🔱 Fork Strategy

• Node Runtime Update
• Node Client Update
• Other:
• N/A

Links

[justinfrevert]

Nice. Might be nice to have the finality checks on other local env runs as well.