LCEssentials installs standalone; each sub target-depends on it so linking a
sub's product always pulls LCEssentials in too, without the consumer having to
declare it separately.
- LCECryptoKit: internalized from the remote LCECryptoKitBinary git dependency
(embedded token URL removed) into a local binaryTarget vendoring
Frameworks/LCECryptoKit.xcframework. LCECryptoKitManager moved out of
LCEssentials core into its own LCECryptoKitManager target/product; the
no-op fallback for when the binary wasn't linked is gone (breaking change
for existing consumers, see decisions/2026-09-15-sub-spm-optional-products.md).
- LCFeatureControl: new product wrapping Atomenta's Feature Control API
(flag evaluation with TTL cache + safe-degrade fallback to defaults,
notifications inbox, batched exposure telemetry). 45 new tests.
