chore: single script to bump the Noir compiler version

[AztecBot]

What

Makes bumping the Noir compiler a single, discoverable, complete operation. One script does everything; the skill and docs just point at it.

Bumping Noir must move several tracked artifacts together, or the tree is inconsistent and CI fails:

1. the noir/noir-repo submodule pointer
2. avm-transpiler/Cargo.lock (the transpiler depends on noir crates by path)
3. yarn-project/yarn.lock (picks up noir JS package version / file: hash changes)
4. noir-projects formatting (a compiler bump can change formatter output)

Changes

• noir/scripts/bump_noir_compiler.sh (new) — the single source of truth. Fetches <ref> into the shallow submodule and checks it out, refreshes Cargo.lock via targeted cargo update -p <noir crates only> (honouring the repo's lockfile-discipline rule), refreshes yarn.lock via yarn install --mode=update-lockfile, reformats noir-projects, and stages all of it. <ref> is a noir-lang/noir ref — release tag v1.0.0-beta.23, nightly nightly-2026-06-02, branch, or commit; no arg → latest nightly-* tag. Stages but does not commit. All the operational knowledge (why targeted cargo update, the expected-version sanity check against .release-please-manifest.json, "don't edit noir/noir-repo to fix the transpiler build", the format-needs-nargo note, git-status-from-root) lives as inline comments on the relevant sections.
• .claude/skills/noir-sync-update — rewrote the description so a "bump the noir compiler version to X" request actually surfaces this skill (the old wording didn't match), and reduced the body to a pointer at the script rather than a parallel set of manual steps. One source of truth, not two.
• CLAUDE.md — <bumping_noir> block points straight at the script (surfaced via the skill).
• .github/workflows/pull-noir.yml — nightly auto-bump PR delegates its submodule + lockfile step to the script. No functional change to its PR-creation behavior.

Notes

The update/format steps need a real toolchain (cargo, corepack/yarn, a built nargo); in a bare checkout each step warns rather than aborting, so a partial run still leaves a useful diff to finish by hand.