Move webhook tests to root tests/ dir and restructure to be non-flaky. Setup webhook capture server once via preload, tear down on process exit. Tests now clean up their own PRs in afterEach. Added bridge test to verify Spike PRs create Discord threads. Made Discord client login explicit via startDiscord(). Updated config with new dev Discord channel and Spike username mappings.
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
