Consolidate Dependabot dependency bumps (#122–#128)

[enricopiovesan]

Summary

Consolidates the seven open Dependabot PRs into one maintainer PR that passes repo CI gates.

• Bump GitHub Actions: actions/checkout v4→v7, actions/setup-node v4→v6
• Bump npm dev deps across all web workspaces: vitest/@vitest/coverage-v8 3→4, jsdom 26→29, @types/node 24→26, typescript-eslint 8.62→8.63
• Replace global with globalThis in unit tests so typecheck passes with Vitest 4 and @types/node 26

No UI or runtime behavior changes — dependency and test typing only. Architecture boundary unchanged: UI remains a rendering layer with no business logic added.

Supersedes #122, #123, #124, #125, #126, #127, #128.

Definition of Done

• All Dependabot bumps from Bump actions/checkout from 4 to 7 #122–Bump @vitest/coverage-v8 from 3.2.6 to 4.1.10 #128 applied in one changeset
• CI workflow action pins updated in .github/workflows/ci.yml and .github/workflows/nightly.yml
• Unit tests updated for Vitest 4 / @types/node 26 compatibility
• Dependabot PRs closed after this PR merges

Validation

npm install
npm run typecheck
npm run lint
npm run test
bash scripts/ci/coverage_gate.sh
bash scripts/ci/repository_checks.sh

All commands pass locally.

Checklist

• Issue linked and Project 2 item updated (maintenance — no feature issue)
• Updated AGENTS.md platform table if this changes platform status (N/A)
• No business logic added to UI layer
• CI gates pass locally where applicable

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