get_peers() was sending no auth headers to /registry/:id/peers — this would
return 401 for every workspace agent after PR #31 (WorkspaceAuth middleware)
deploys, breaking peer discovery entirely.
discover_peer() had X-Workspace-ID but was missing the bearer token, also
required by Phase 30.6 for /registry/discover/:id.
Both functions now send {"X-Workspace-ID": WORKSPACE_ID, **auth_headers()}.
get_workspace_info() was already correct (auth_headers() present since PR #39).
Adds test_request_sends_workspace_id_header to TestGetPeers; hardens the
discover_peer header assertion to use presence-check rather than exact equality.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>