chore: Refactor test targets (#2583)

## Why is this change needed?

Cleans up how we define our various build targets.

## Merge Checklist

- [x] PR title adheres to the [conventional
commits](https://www.conventionalcommits.org/en/v1.0.0/) standard
- [ ] PR has a
[changeset](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#35-adding-changesets)
- [ ] PR has been tagged with a change label(s) (i.e. documentation,
feature, bugfix, or chore)
- [ ] PR includes
[documentation](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#32-writing-docs)
if necessary.


<!-- start pr-codex -->

---

## PR-Codex overview
This PR focuses on updating the CI configuration in the
`.github/workflows/ci.yml` file to support a matrix strategy for
different architectures and Node.js versions.

### Detailed summary
- Changed `arch` from individual entries to a list: `['arm64', 'x64']`.
- Updated `node_version` to support multiple versions: `[22, 24]`.
- Adjusted `runs-on` to dynamically use `matrix.arch`.

> ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your
question}`

<!-- end pr-codex -->

.github/workflows/ci.yml

@@ -18,15 +18,10 @@ jobs:
 
     strategy:
       matrix:
-        include:
-          - arch: 'arm64'
-            node_version: 22.4.1
-            runs_on: ['runs-on=${{ github.run_id }}', 'runner=4cpu-linux-arm64']
-          - arch: 'x64'
-            node_version: 22.4.1
-            runs_on: ['runs-on=${{ github.run_id }}', 'runner=4cpu-linux-x64']
+        arch: ['arm64', 'x64']
+        node_version: [22, 24]
 
-    runs-on: ${{ matrix.runs_on }}
+    runs-on: ['runs-on=${{ github.run_id }}', 'runner=4cpu-linux-${{ matrix.arch }}']
     name: test (Node ${{ matrix.node_version }}, ${{ matrix.arch }})
 
     services: