Several worlds: a Worlds list with load, rename and delete; old save migrates to World 1

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/PROJECT_MAP.md

@@ -369,16 +369,16 @@ The title screen art.
 - functions: buildTitleCells, drawTitle
 - variables: FONT5, TITLE
 
-### src/ui/saves.js (106 lines)
+### src/ui/saves.js (177 lines)
 Saves in IndexedDB, world files (export / import) and the blueprint library.
-- functions: saveWorld, newestSave, b64FromBytes, bytesFromB64, gz, exportWorld, importWorldFile, libLoad, libSave, bpEncode, bpValid, bpDecode
-- variables: DB
+- functions: newWorldId, worldWrite, listWorlds, putWorldEntry, worldNewest, deleteWorld, renameWorld, migrateWorlds, saveWorld, newestSave, b64FromBytes, bytesFromB64, gz, exportWorld, importWorldFile, libLoad, libSave, bpEncode, bpValid, bpDecode
+- variables: DB, worldIdTime, worldIdCounter, worldWrites
 
-### src/ui/session.js (87 lines)
+### src/ui/session.js (122 lines)
 Starting, loading and quitting a game; modal dialogs; the pause menu.
-- functions: showLoading, enterGame, startNewWorld, startFromSave, quitToTitle, refreshContinue, anyModal, openModal, closeModal, closeAllModals, topModal, dialog, openPause
+- functions: showLoading, enterGame, startNewWorld, startFromSave, quitToTitle, refreshContinue, anyModal, openModal, closeModal, closeAllModals, topModal, dialog, openPause, renderWorlds
 
-### src/ui/settings.js (116 lines)
+### src/ui/settings.js (122 lines)
 The settings screen.
 - functions: openSettings, renderSettings, applySettings, toggleFullscreen, confirmWipe
 - variables: SET_TABS, setTab
@@ -430,7 +430,7 @@ Previews drawn under the cursor: build ghosts, drill aim and pulses, selections,
 Events from the simulation (emit) turned into sounds, toasts and cards.
 - functions: drainEvents
 
-### src/ui/loop.js (117 lines)
+### src/ui/loop.js (119 lines)
 The frame loop and boot.
 - functions: scanVisible, frame, boot
 - variables: lastT, acc, lastRender, frameMs, simMs, fpsSm, ambientT