Make catalog feed configuration optional and explicit

docs/CURRENT-STATE.md

@@ -1,5 +1,15 @@
 # God's Eye View Current State
 
+Catalog source contracts and their consuming layers are declared in
+`src/app/sourceComposition.js`. Omitted or null acquisition sources preserve layer
+registration and serialization, report unavailable, and are refused by the existing
+visibility lifecycle before initialization. Invalid supplied methods still fail
+construction. `createStandaloneApplication` and `createStandaloneCatalog` accept
+`sources` overrides; unspecified entries retain
+standalone defaults, and null entries explicitly remove a source. Street Level
+continues to accept an explicit provider list. Directions and Recent Imagery
+acquisition are still selected by their application constructors.
+
 Application catalog composition accepts an optional `streetLevelProviders` list.
 An explicit list replaces the default Mapillary provider; an empty list removes
 all imagery providers. Without that option, Mapillary is registered only when