feat(platform): add NX capability detection module

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

src/core/Platform.lua

@@ -0,0 +1,54 @@
+-- Platform capability detection for NX / mobile / desktop.
+
+local Platform = {}
+
+local cached
+
+local function compute()
+  local osName = (love and love.system and love.system.getOS and love.system.getOS())
+    or "Unknown"
+  local nx = osName == "NX"
+  local mobile = osName == "Android" or osName == "iOS"
+  local nativePicker = love and love.system
+    and type(love.system.pickFile) == "function"
+  return {
+    os = osName,
+    nx = nx,
+    mobile = mobile,
+    console = nx,
+    hasNativePicker = nativePicker,
+    canSpawnProcess = osName == "OS X" or osName == "Windows" or osName == "Linux",
+    romImportMode = nx and "save-directory"
+      or (nativePicker and "native-picker")
+      or "desktop",
+    networkValidated = not nx,
+  }
+end
+
+function Platform.detect()
+  if not cached then cached = compute() end
+  return cached
+end
+
+function Platform.isNX()
+  return Platform.detect().nx
+end
+
+function Platform.romImportMode()
+  return Platform.detect().romImportMode
+end
+
+function Platform.canSpawnProcess()
+  return Platform.detect().canSpawnProcess
+end
+
+function Platform.networkValidated()
+  return Platform.detect().networkValidated
+end
+
+-- Tests may swap love.system between cases.
+function Platform._resetForTests()
+  cached = nil
+end
+
+return Platform

tests/platform_nx_test.lua

@@ -0,0 +1,62 @@
+-- NX / Android / desktop capability detection (SWNX-01).
+-- Self-contained: luajit tests/platform_nx_test.lua
+
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+local T = require("tests.harness")
+local check = T.check
+local eq = T.eq
+
+local savedLove = _G.love
+
+local function withOS(osName, pickFile, fn)
+  _G.love = {
+    system = {
+      getOS = function() return osName end,
+      pickFile = pickFile,
+    },
+  }
+  package.loaded["src.core.Platform"] = nil
+  local Platform = require("src.core.Platform")
+  Platform._resetForTests()
+  local ok, err = pcall(fn, Platform)
+  _G.love = savedLove
+  package.loaded["src.core.Platform"] = nil
+  if not ok then error(err) end
+end
+
+-- NX: save-directory import, no shell spawn, network gated off
+withOS("NX", nil, function(Platform)
+  local caps = Platform.detect()
+  eq(caps.os, "NX", "NX detect os")
+  eq(caps.nx, true, "NX flag")
+  eq(caps.romImportMode, "save-directory", "NX romImportMode")
+  eq(caps.canSpawnProcess, false, "NX cannot spawn processes")
+  eq(caps.networkValidated, false, "NX network not validated")
+  eq(Platform.isNX(), true, "isNX convenience")
+  eq(Platform.romImportMode(), "save-directory", "romImportMode helper")
+end)
+
+-- Android: mobile native picker path, not NX semantics
+withOS("Android", function() end, function(Platform)
+  local caps = Platform.detect()
+  eq(caps.os, "Android", "Android detect os")
+  eq(caps.nx, false, "Android is not NX")
+  eq(caps.mobile, true, "Android mobile")
+  eq(caps.hasNativePicker, true, "Android has pickFile")
+  eq(caps.romImportMode, "native-picker", "Android romImportMode")
+  eq(Platform.isNX(), false, "Android isNX false")
+end)
+
+-- Desktop Linux: shell spawn + desktop import mode
+withOS("Linux", nil, function(Platform)
+  local caps = Platform.detect()
+  eq(caps.os, "Linux", "Linux detect os")
+  eq(caps.nx, false, "Linux is not NX")
+  eq(caps.canSpawnProcess, true, "Linux can spawn processes")
+  eq(caps.romImportMode, "desktop", "Linux romImportMode")
+  eq(caps.networkValidated, true, "Linux network validated")
+  eq(Platform.canSpawnProcess(), true, "canSpawnProcess helper")
+end)
+
+T.finish()

tests/run_tests.lua

@@ -3369,6 +3369,8 @@ runSuites({ "tests/rom_importer_android_mod_pick_test.lua" })
 -- ---------------------------------------------- import with no picker (#482)
 runSuites({ "tests/rom_importer_no_picker_test.lua" })
 runSuites({ "tests/rom_importer_double_pick_test.lua" })
+-- ---------------------------------------------- Switch platform capabilities
+runSuites({ "tests/platform_nx_test.lua" })
 -- ---------------------------------------------- parity workstream tests
 -- Each tests/parity_*.lua is a self-contained file (own bootstrap + check,
 -- error()s if any assertion fails).  Globbed, so dropping a new parity