chore(dev-env): warn when local Node major diverges from CI's pinned version

[carlos-alm]

Summary

• A fresh worktree on a machine running a Node major version CI doesn't pin (e.g. Node 26, when .github/workflows/ci.yml pins Node 22 everywhere) can produce 200+ unrelated-looking local test failures from native-addon/V8 behavioral drift, not actual regressions — the failures reproduce identically on an untouched origin/main checkout in the same environment, wasting time triaging phantom failures or masking a real one in the noise.
• Adds .nvmrc (22, mirroring every node-version: 22 in ci.yml) as a single reference point, plus a new checkNodeVersion doctor check wired into the existing pretest-gated npm run doctor, that warns — never fails, since a mismatch doesn't mean the environment is broken, just that local results shouldn't be trusted over CI's — when the running Node major doesn't match it.
• Documents the cross-check guidance in CLAUDE.md's Node Version section, per the issue's first suggested fix.
• Deliberately does not change ci.yml itself to read from .nvmrc (e.g. via actions/setup-node's node-version-file) — that would be a genuine further step toward eliminating the duplication entirely, but is a separate, more invasive change to a critical shared workflow file that the issue didn't ask for. Filed as a follow-up.

Test plan

• New tests in tests/unit/doctor.test.ts: no .nvmrc present, unparseable .nvmrc content, exact major match, full-semver .nvmrc with matching major, leading-v/trailing-comment tolerance, a genuine mismatch (warns, never fails), and that the warning doesn't flip runDoctorChecks' overall report unhealthy.
• Live sanity check on this actual machine (Node v26.4.0, .nvmrc pins 22): npm run doctor now correctly prints the warning — this is the exact repro from the issue.
• Full npx vitest run (5514 tests) and npm run lint clean.
• npm run build (TypeScript) clean.

Closes #2521

[greptile-apps]

Greptile Summary

Adds a non-blocking doctor diagnostic for local Node-major divergence from CI.

• Adds .nvmrc pinning Node 22.
• Reads that pin during npm run doctor and warns when the running major differs.
• Documents the local-versus-CI cross-check guidance.
• Adds unit coverage for parsing, matching, mismatches, and report aggregation.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The new diagnostic resolves the repository root correctly in its current source and compiled layouts, reads the tracked Node pin, reports major mismatches without making the doctor report unhealthy, and is covered across its intended input states.

Important Files Changed

Filename	Overview
src/infrastructure/doctor.ts	Adds repository-local .nvmrc reading, major-version comparison, and a non-blocking warning to the existing doctor report.
tests/unit/doctor.test.ts	Covers absent and unparseable pins, supported version forms, matching and mismatching majors, and warning aggregation.
.nvmrc	Establishes Node 22 as the local version-manager reference matching CI’s major pin.
CLAUDE.md	Documents how developers should interpret local test failures when their Node major differs from CI.

_{Reviews (1): Last reviewed commit: "chore(dev-env): warn when local Node maj..." | Re-trigger Greptile}

[github-actions]

Codegraph Impact Analysis

4 functions changed → 3 callers affected across 2 files

• parseNvmrcMajor in src/infrastructure/doctor.ts:328 (3 transitive callers)
• readNvmrc in src/infrastructure/doctor.ts:336 (0 transitive callers)
• checkNodeVersion in src/infrastructure/doctor.ts:359 (2 transitive callers)
• runDoctorChecks in src/infrastructure/doctor.ts:407 (1 transitive callers)