Include E2E spec glob in testing-guidelines rule

[dyoshikawa]

Motivation

• Ensure the testing guidelines also apply to end-to-end spec files under src/e2e/**/*.spec.ts so E2E tests follow the same conventions as unit tests.

Description

• Update frontmatter in .rulesync/rules/testing-guidelines.md to add src/e2e/**/*.spec.ts to the globs list alongside the existing **/*.test.ts pattern.

Testing

• Ran pnpm cicheck, which runs format checks, linters, type checks, vitest tests, cspell, and secretlint, and all checks passed; vitest reported 180 test files and 4845 tests passed.

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Codex Task

[Copilot]

Pull request overview

Updates the Rulesync testing guidelines rule so the same conventions apply to end-to-end (E2E) spec files under src/e2e/**/*.spec.ts, aligning E2E tests with existing unit-test conventions.

Changes:

• Expanded the .rulesync/rules/testing-guidelines.md frontmatter globs to include src/e2e/**/*.spec.ts in addition to **/*.test.ts.