ci(functional-tests): reserve node 0 for serialized phone tests

[nshirley]

Because:

• Node 0 was doing double duty: running the serialized #phone tests AND receiving its share of the timings-based split, making it the long pole that gated the whole functional-test job.

This commit:

• Makes run-playwright-tests reserve node 0 for the serialized #phone tests whenever #phone is grep-inverted out of the split and there is more than one node. Node 0 then skips the split (its phone tests already ran) and the split is redistributed across the remaining nodes via --total/--index shifted down by one.
• Infers the reservation from the existing grep_invert: '#phone' signal rather than a separate flag, so payments and single-node smoke jobs (which run no phone tests) keep the full split unchanged.
• Uses exit 0 (not step halt) so node 0 still stores/uploads its phone-test artifacts.

Closes: (issue number)

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
• I have manually reviewed all AI generated code.

How to review (Optional)

• Key files/areas to focus on:
• Suggested review order:
• Risky or complex parts:

Screenshots (Optional)

Please attach the screenshots of the changes made in case of change in user interface.

Other information (Optional)

Any other information that is important to this pull request.

[Copilot]

Pull request overview

Updates the CircleCI Playwright functional-test splitting so that when #phone tests are run serially on node 0, node 0 is removed from the timings-based split and the remaining nodes pick up the redistributed workload.

Changes:

• Skip running split Playwright tests on node 0 when #phone tests are excluded and the job is running with parallelism > 1.
• Redistribute the CircleCI timing split across nodes 1..N by shifting --total/--index down by one.
• Clarify the relationship between serialized phone tests and the split (comment update).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.