build(lint): bump default prettier pin to 3.9.4

[bryanfawcett]

Summary

• Bumps the default prettier-version in reusable-lint.yml from 3.8.4 to 3.9.4 (current latest on npm).
• Verified with prettier@3.9.4 --check "**/*.{md,mdx,json,jsonc}" against this repo's own files — all pass with no reformatting needed, and the upstream changelog has no breaking changes for Markdown/JSON/JSONC in this range.

Linked issue(s)

Closes #

Type of change

• build — build system, packaging, dependencies

Breaking change?

• This PR introduces a breaking change.

How has this been tested?

Ran npx prettier@3.9.4 --check "**/*.{md,mdx,json,jsonc}" locally against the full repo: All matched files use Prettier code style!

Checklist

Process

• My PR title follows Conventional Commits.
• All of my commits are signed (SSH) and show "Verified" on GitHub.
• All of my commits have a DCO sign-off (Signed-off-by: trailer, human operator identity).
• My branch name follows the agent convention (claude/<short-kebab-description>).
• I have rebased onto the latest default branch; no merge commits.
• Tests — N/A, this is a version-pin bump for an existing reusable workflow input; verified via local prettier --check run above.
• Documentation — N/A, no behavior or interface change.
• I ran the repo's local checks (prettier --check) and they pass.
• No new runtime dependencies.
• Not a breaking change.

NA-03 merge blockers

• N/A — this change does not touch schema, APIs, dependencies (other than a lint-tool patch version), cryptography, data placement, or smart-contract counts.

Additional notes

While auditing this repo for currency, I found a separate, more significant issue that I'm not fixing in this PR because it's ambiguous and CI/CD-pipeline-affecting (NA-03 §7.1.1 / escalation criteria):

actions/checkout SHA pins are inconsistent and one set is mislabeled. The most recent Dependabot bump (build(deps): bump the all group with 10 updates (#29)) moved 15 of the 18 workflow files in .github/workflows/ from actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd (which is genuinely v6.0.2) to actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 — but that SHA is actually v7.0.0 (tagged 17 Jun 2026), not v6. The trailing comment on all 15 was left as # v6, which violates the NA-03 §7.1.1 requirement that the comment accurately record the version. The other 3 files (reusable-ci-docker.yml, reusable-ci-terraform.yml, reusable-ci-typescript-lib.yml) are still on the older, genuine v6.0.2 SHA — so the org's reusable workflows are currently split between an unreviewed v7 and a stale v6.0.2, with neither state fully intentional.

actions/checkout v7 is a major bump (ESM rewrite, and it now blocks checkout of fork-PR code by default for pull_request_target/workflow_run triggers unless allow-unsafe-pr-checkout: true is set) — the kind of change NA-03 §7.1.2/§5.1 implies should get a deliberate look rather than ride in silently inside a grouped "bump the all group" Dependabot PR. I'd rather flag this for a maintainer to decide (embrace v7 org-wide with corrected # v7.0.0 comments, or pin everything back to genuine v6.0.3 — current SHA df4cb1c069e1874edd31b4311f1884172cec0e10) than pick a direction myself in an unattended run. Happy to open that as a follow-up PR once there's a decision.

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