GLSP-1635: Migrate spec assertions to native Vitest matchers

[tortmayr]

What it does

Follow-up to the Vitest migration (#1705): converts the remaining chai-style
BDD assertions in all spec files to native Vitest matchers and drops the
now-unused chai tooling.

• Migrate all spec assertions across 35 files (.to.equal → toBe,
  .to.deep.equal → toEqual, .to.include.members([...]) →
  toEqual(expect.arrayContaining([...])), .to.throw → toThrow, etc.)
• Remove eslint-plugin-chai-friendly from the config and eslint-config
  packages and re-enable the core no-unused-expressions rule, which is correct
  again now that assertions are function calls rather than property accesses
• Drop the obsolete globals.mocha entry from the base ESLint config
• Remove stale ctrf/ and .nyc_output/ entries from .gitignore
• Add a test:coverage passthrough script to the root package.json

Part of: #1635

How to test

pnpm install
pnpm test

• Full CLI unit suite passes (22 files, 395 tests) — verified locally
• No chai/mocha/sinon references remain in dev-packages/cli/src or tests

Follow-ups

Changelog

• This PR should be mentioned in the changelog
• This PR introduces a breaking change (if yes, provide more details below for the changelog and the migration guide)

[Copilot]

Pull request overview

This PR completes the Vitest migration by converting the remaining chai-style assertions in CLI unit/e2e specs to native Vitest matchers, and cleans up the now-obsolete ESLint/ignore tooling that supported chai’s property-based assertions.

Changes:

• Migrate chai-style assertions to Vitest matchers across CLI unit and e2e spec files.
• Remove eslint-plugin-chai-friendly, re-enable core no-unused-expressions, and drop obsolete globals.mocha from the shared ESLint config.
• Minor repo hygiene: remove stale ignore entries and add a root test:coverage passthrough script.

Reviewed changes

Copilot reviewed 37 out of 39 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pnpm-lock.yaml	Removes eslint-plugin-chai-friendly from the lockfile/importers.
package.json	Adds root test:coverage script forwarding to dev-packages/cli.
dev-packages/eslint-config/package.json	Drops eslint-plugin-chai-friendly peer dependency.
dev-packages/eslint-config/configs/errors.js	Re-enables core no-unused-expressions with appropriate options.
dev-packages/eslint-config/configs/base.js	Removes chai-friendly plugin wiring and obsolete globals.mocha.
dev-packages/config/package.json	Drops eslint-plugin-chai-friendly dependency.
dev-packages/cli/tests/e2e/update-next.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/repo/repo-vscode.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/repo/repo-theia.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/repo/repo-eclipse.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/repo/repo-core-clone.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/repo/repo-core-build.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/releng/version.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/releng/prepare.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/generate-index.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/tests/e2e/check-header.e2e.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/util/validation-util.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/util/process-util.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/util/package-util.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/util/glsp-repo-util.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/util/git-util.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/util/file-util.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/update-next.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/workspace.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/switch.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/start.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/server-node.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/run.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/repo.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/link.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/fork.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/common/utils.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/clone.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/repo/build.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/releng/version.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/releng/publish.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/commands/releng/common.spec.ts	Converts assertions to Vitest matchers.
dev-packages/cli/src/cli.spec.ts	Converts assertions to Vitest matchers (CLI shape/option tests).
.gitignore	Removes stale ctrf/ and .nyc_output/ ignore entries.

Files not reviewed (1)

• pnpm-lock.yaml: Generated file

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