자체 구현이 먼저, 연결은 나중

# The engine runs on service host beside cwkPippa and reaches it over loopback,
# like Forge, Vesta and Waystone. Loopback is outside macOS 26's Local
# Network gate and is the boundary cwkPippa trusts without a PIN; a
# tailnet origin here answers 401 pin_required (Easel, 2026-09-25).
PIPPA_BASE = os.environ.get("SIZZLE_PIPPA_BASE", loopback_origin("cwkPippa")).rstrip("/")

# Brains are global family settings held by the Brain Control Plane, reached
# through Firelink's facade on loopback like every engine on service host. Sizzle's
# Settings page and Firelink's Brains tab edit the same per-function slots
# (brain_control.py). These two values only seed the reading slot's first
# registration; after that central is the only truth.
FAMILY_CONTROL_BASE = os.environ.get("SIZZLE_FAMILY_CONTROL_BASE", loopback_origin("cwkFirelink")).rstrip("/")

$ git grep -n -E 'cwksizzle://|kit_item_ref|link_app' origin/main -- .
origin/main:docs/SIZZLE-ARCHITECTURE.md:260:(cwkSiblingKit SIBLING-CONTRACTS §16, `kit_item_ref.py`) is `{app, kind,
origin/main:docs/SIZZLE-ARCHITECTURE.md:262:Spark receives links on the web (`/?link_app&link_kind&link_id&link_parent&link_label`)
origin/main:docs/SIZZLE-ARCHITECTURE.md:286:   and a `cwksizzle://` scheme in SizzleMobile, neither of which exists yet.
$ git grep -n 'CFBundleURLTypes' origin/main -- clients; echo "exit $?"
exit 1
$ git ls-tree --name-only origin/main backend/ | grep kit_
backend/kit_atomic_file.py
backend/kit_brain_control.py
backend/kit_brain_control_routes.py
backend/kit_brain_control_testing.py
backend/kit_log_format.py
backend/kit_pippa.py
backend/kit_pippa_brains.py
backend/kit_pippa_uploads.py
backend/kit_product_version.py
backend/kit_staged_uploads.py
backend/kit_ulid.py
backend/kit_webui_static.py

"""The family item reference: point at another app's item, never copy it.

Canonical here; the contract is SIBLING-CONTRACTS §16. A reference is
``{app, kind, id, parent}``: the owning app, its own word for the item, the
item's id, and the container the id is unique within when it is not unique
alone (a Waystone crumb id is unique inside its journey; a Vesta crumb id is
unique across journals and survives a move, so it carries no parent).

The linking app stores the reference, and at most a label it saw when the
link was made; everything else is asked of the owner when it is shown
(Forge's and Vesta's no-warehouse rule). :func:`resolve` asks the owner's
one-item route and folds the answer into one card shape, so a linking
surface draws a Waystone crumb, a Vesta crumb and a Spark moment the same way.