test: keep jsdom's localStorage under Node 26

[fernandomg]

Summary

Closes #132

On Node 26 every vitest suite in the repo fails before its first assertion. Node now ships localStorage as a global, and vitest 4 keeps a global it already finds instead of copying jsdom's, so the tests get undefined. engines.node has no upper bound, so Node 26 is supported on paper, and CI never ran it.

Changes

• Vitest workers start with --no-experimental-webstorage, so jsdom's localStorage lands on Node 26 as it does on 24
• CI runs the test suites on Node 26 beside the pinned 24

Deviations

• The issue names canton-connect; the same cause also fails canton-dappbooster and dapp/frontend, so all three configs change
• A Node flag per vitest config instead of the issue's in-memory polyfill: nothing hand-written, and it goes when vitest 5 lands, where this is fixed upstream
• The Node 26 CI job is extra scope; requiring it is a ruleset edit after merge

Acceptance criteria

• Suite passes on any Node satisfying engines.node

Test plan

Automated tests

1. On main under Node 26 (nvm use 26), run pnpm test; expect failures in every suite with Cannot read properties of undefined
2. Check out this branch and run pnpm test; expect every suite green
3. Run nvm use (Node 24 from .nvmrc) and pnpm test again; expect the same

Manual verification

1. Open the Checks tab of this PR
2. Expect 3 - test (node 26) green beside 3 - test

Breaking changes

None.

Checklist

• Self-reviewed my own diff
• Tests added or updated
• Docs updated (if applicable)
• No unrelated changes bundled in

Screenshots

None.

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Project	Deployment	Actions	Updated
demo.canton-dappbooster	Ready	Preview	Sep 3, 2026 5:00pm UTC
docs.canton-dappbooster	Ready	Preview	Sep 3, 2026 5:00pm UTC

[Copilot]

🔵 Needs a closer look

It modifies the CI/CD workflow, which the repository guardrails state must not be changed without team review, and it carries a documented manual follow-up (making the new job a required check via a ruleset edit).

Pull request overview

This PR fixes a test-environment regression that surfaces on Node 26. Node 25+ ships localStorage as a global by default, and under vitest 4 the test runner keeps a global it already finds rather than copying jsdom's, so every suite gets Node's storage (which returns undefined without --localstorage-file) and fails before its first assertion. The fix passes --no-experimental-webstorage to the vitest worker processes so jsdom's localStorage is used, restoring the Node 24 behavior. It also adds a CI job that runs the suites on Node 26 alongside the pinned Node 24, since engines.node has no upper bound and Node 26 was never exercised.

I verified the approach is sound: test.execArgv is a valid top-level option in vitest 4 (poolOptions were flattened to top-level in v4), and --experimental-webstorage has existed since Node 22.4.0, so --no-experimental-webstorage is accepted (and a harmless no-op) on the pinned Node 24.15+ while disabling the shadowing global on Node 25/26. The new CI job mirrors the existing test job exactly, differing only in the Node version.

Changes:

• Add execArgv: ['--no-experimental-webstorage'] to the three jsdom vitest configs (canton-connect, canton-dappbooster, dapp/frontend) with an explanatory comment.
• Add a test-node-26 CI job to .github/workflows/pr.yml running pnpm test on Node 26.

File summaries

File	Description
canton-connect/vitest.config.ts	Passes --no-experimental-webstorage to workers so jsdom's localStorage is used under Node 26.
canton-dappbooster/vitest.config.ts	Same flag; this suite's afterEach calls localStorage.clear(), which depends on jsdom's storage.
dapp/frontend/vite.config.ts	Same flag added to the nested vitest test block (its LedgerBackend tests touch localStorage).
.github/workflows/pr.yml	Adds a test-node-26 job that runs the suites on Node 26 beside the pinned Node 24 job.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Balanced

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[pablofullana]

LGTM 👍