fix(#397): guard the gh-pr-edit workaround, since the repo cannot fix gh itself

[TortoiseWolfe]

gh pr edit fails on every invocation against this repo. Its GraphQL pre-fetch asks for
repository.pullRequest.projectCards — a Projects (classic) field GitHub has sunset — so the
server rejects the whole query before any edit is attempted.

Re-verified today, probed with a deliberately invalid label so nothing could mutate:

$ gh pr edit 806 --repo TortoiseWolfe/ScriptHammer --add-label "zz-not-a-real-label-397-probe"
GraphQL: Projects (classic) is being deprecated ... (repository.pullRequest.projectCards)
exit 1

gh issue edit, gh pr merge and gh api are unaffected.

This is Refs, not Closes — deliberately

The repo cannot fix it. The bug is in the CLI's own query, and gh 2.46.0 is from January
2025. The remaining action is an environment change — upgrade gh — so #397 stays open, and is
retitled to say that rather than reading as a repo defect somebody could go fix in here.

What the repo can do, and now does

scripts/__tests__/gh-pr-edit-is-avoided.test.js (in pnpm test:scripts, so inside the required
Test (20.x) check) asserts:

1. no script, workflow or hook calls gh pr edit — distinguishing a call site from prose,
   so CLAUDE.md and the test itself can still name the command out loud;
2. CLAUDE.md still carries the REST workaround, in runnable form, so a docs tidy cannot leave
   the warning standing without its remedy.

Why a test and not just the note

The failure is quiet in the way that matters: non-zero exit, but a message that reads like a
deprecation notice, on stderr. Wrapped as cmd >/dev/null 2>&1 && echo ok || echo FAILED it
reports FAILED with no visible reason — which is exactly how it was originally found, one line
in a batch of five that looked like an unrelated permissions problem. A script that adopted
gh pr edit would keep working right up until it silently stopped.

Mutation-verified, both halves

mutation	result
add a real call site	fails naming scripts/ci/zz-mutant.sh:2
replace the gh api -X PATCH line in CLAUDE.md	fails with "the warning is not actionable"

Controls prove the detector separates prose from a call site in both directions — a guard that
flagged the documentation would be deleted by the first person it annoyed.

To close #397

Upgrade gh, re-run the probe above, and if it succeeds delete both the CLAUDE.md note and this
test. That test failing after an upgrade is the signal the workaround is no longer needed —
not a regression.

pnpm test:scripts: 374 passed

Refs #397