Fix four failing backend test files in Release CI

[Copilot]

Four test files were failing with assertion errors (ERR_ASSERTION) and type errors due to missing vscode mock entries, a missing method invocation, broken JSDOM initialization, and missing HTML content the tests expected.

Changes

vscode-shim-register.ts

• Added ViewColumn enum (needed by BackendConfigPanel.show())
• Added Uri.joinPath() static method (needed by renderHtml())

backend-cache-integration.test.ts

• The "validates cached data" loop was creating a BackendFacade but never invoking computeDailyRollupsFromLocalSessions() — no warnings were ever generated, so all assert.ok(warnings.some(...)) checks failed

backend-configurator.test.ts

• Set window.__toolkitReady = true in all three JSDOM beforeParse callbacks so waitForToolkit() immediately calls init() and wires up event listeners. Without this, the change event on authMode had no handler.
• Fixed HTML sanitization regex: the old pattern /toolkit\.js"><\/script>/ matched only src= script tags. The actual HTML uses an inline module script (await import('toolkit.js')), which was left in and caused JSDOM to attempt network fetches:

  // Before (missed inline module script):
  html.replace(/<script type="module"[^>]*toolkit\.js"><\/script>/, '')
  // After (removes all module scripts):
  html.replace(/<script type="module"[\s\S]*?<\/script>/g, '')

• Changed querySelector('#overview .helper') → querySelectorAll(...).some(h => h.includes('Stay Local')) since the matching text is not in the first helper element
• Added dom.window.close() after each JSDOM test's assertions

src/backend/configPanel.ts

• Added a "Stay Local" helper paragraph to the overview section — the test expected this copy to exist there

Original prompt

The CI workflow 'Release' is failing due to test failures. The following tests fail with errors such as 'Expected values to be strictly equal' and 'The expression evaluated to a falsy value':

• out/test/test-node/backend-commands.test.js
• out/test/test-node/backend-copyConfig.test.js
• out/test/test-node/backend-configurator.test.js
• out/test/test-node/backend-cache-integration.test.js

Tasks:

1. Review each failing test and the corresponding implementation code.
2. Update code or tests as necessary to ensure all assertions pass, matching expected and actual values appropriately.
3. Ensure all required mocks, test data, and conditions are up to date.
4. Re-run tests to verify that the failures have been resolved.

Goal: The 'Release' workflow should complete successfully without test failures.

This pull request was created from Copilot chat.

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