fix(switch): pass NX cache prefix to the chip-audio worker

Yellow music was still silent because the background worker thread loads
ChipSynth.lua in a fresh Lua state with no GameVersion/Platform context.
The main thread's prefix never reached it.

ChipAudio.slimAudio now resolves the versioned cache prefix on the main
thread and includes it in the audio payload as `programPrefix`.
ChipSynth.loadBanks prefers `audio.programPrefix` when present, falling
back to its own NX detection for the sync path. Blue and Yellow are
handled the same way.

Tests cover the worker prefix hand-off and Blue's programs.bin path.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/core/ChipAudio.lua

@@ -100,14 +100,27 @@ end
 -- play so a hot-reloaded dataset (or a mod's audio) always reaches the worker
 local function slimAudio(data)
   local audio = data.audio or {}
+  -- NX-only: resolve the versioned cache prefix on the main thread and hand
+  -- it to the worker, which runs in a fresh Lua state without GameVersion.
+  local programPrefix
+  if require("src.core.Platform").isNX() then
+    local prefix = require("src.core.GameVersion").cachePrefix()
+    if prefix ~= "" then programPrefix = prefix end
+  end
   return {
     programFile = audio.programFile,
+    programPrefix = programPrefix,
     bankOrder = audio.bankOrder,
     waveBanks = audio.waveBanks,
     noiseHeaders = audio.noiseHeaders,
   }
 end
 
+-- test-only: expose slimAudio so the NX prefix hand-off is verifiable
+function ChipAudio._slimAudioForTest(data)
+  return slimAudio(data)
+end
+
 -- If the worker died (a malformed def that errors mid-synth), fall back to the
 -- synchronous path for the rest of the session instead of going silent.
 local function workerAlive()

src/core/ChipSynth.lua

@@ -124,13 +124,16 @@ local function loadBanks(data)
     return cachedBanks
   end
   local raw, readError
-  -- NX-only: Blue/Yellow live under a versioned save-dir prefix; desktop
+  -- NX-only: Blue/Yellow live under a versioned save-dir prefix. The main
-  -- relies on mountVersion overlay. Read the prefixed path when present.
+  -- thread resolves it before sending audio to the worker; the sync path
-  if require("src.core.Platform").isNX() then
+  -- resolves it here so desktop keeps the mountVersion overlay behavior.
-    local prefix = require("src.core.GameVersion").cachePrefix()
+  local prefix = audio.programPrefix
-    if prefix ~= "" then
+  if not prefix and require("src.core.Platform").isNX() then
-      raw, readError = love.filesystem.read(prefix .. audio.programFile)
+    local gv = require("src.core.GameVersion").cachePrefix()
-    end
+    if gv ~= "" then prefix = gv end
+  end
+  if prefix and prefix ~= "" then
+    raw, readError = love.filesystem.read(prefix .. audio.programFile)
   end
   if not raw then
     raw, readError = love.filesystem.read(audio.programFile)

tests/engine/assets_version_fallback_test.lua

@@ -111,6 +111,42 @@ if okB and banks then
   eq(banks[1], PROG_BYTES:sub(1, 0x4000), "loadBanks returns the bank 1 bytes")
 end
 
+-- ChipSynth honors an explicit programPrefix (worker path; worker has no
+-- GameVersion state, so the prefix must arrive via the audio payload)
+ChipSynth.invalidateBanks()
+local workerData = { audio = {
+  programFile = PROG,
+  programPrefix = "yellow/",
+  bankOrder = { 1, 2 },
+} }
+local okW, wbanks = pcall(ChipSynth._loadBanksForTest, workerData)
+check(okW and wbanks ~= nil, "loadBanks uses audio.programPrefix when set")
+if okW and wbanks then
+  eq(wbanks[1], PROG_BYTES:sub(1, 0x4000),
+    "programPrefix loads the same bank 1 bytes")
+end
+
+-- Blue gets the same treatment
+ChipSynth.invalidateBanks()
+GameVersion.set("blue")
+love.filesystem.write("blue/" .. PROG, PROG_BYTES)
+clearPath("yellow/" .. PROG)
+local okBl, bbanks = pcall(ChipSynth._loadBanksForTest, progData)
+check(okBl and bbanks ~= nil, "NX loadBanks reads blue/programs.bin")
+clearPath("blue/" .. PROG)
+GameVersion.set("yellow")
+love.filesystem.write("yellow/" .. PROG, PROG_BYTES)
+
+-- ChipAudio.slimAudio hands the NX prefix to the worker
+local ChipAudio = require("src.core.ChipAudio")
+local slim = ChipAudio._slimAudioForTest
+  and ChipAudio._slimAudioForTest(progData)
+  or nil
+if slim then
+  eq(slim.programPrefix, "yellow/",
+    "slimAudio passes the NX cache prefix to the worker")
+end
+
 -- Sound.playPikaCry: NX rewrites the pika-cry path before newSource
 setOS("NX")
 GameVersion.set("yellow")