fix(platform): skip host shell spawn on NX

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

tests/platform_nx_shell_gate_test.lua

@@ -0,0 +1,55 @@
+-- NX must not invoke HostShell / desktop file pickers (SWNX-04).
+package.path = "./?.lua;./?/init.lua;" .. package.path
+if not _G.love then _G.love = require("tests.love_stub") end
+love.system = love.system or {}
+love.filesystem = love.filesystem or {}
+
+local S = require("tests.harness").suite("platform NX shell gate")
+local check = S.check
+local eq = S.eq
+
+local popenCalls = 0
+local realHostShell = package.loaded["src.core.HostShell"]
+package.loaded["src.core.HostShell"] = {
+  envPrefix = function() return "" end,
+  popen = function()
+    popenCalls = popenCalls + 1
+    return nil
+  end,
+  restart = function() end,
+}
+
+love.system.getOS = function() return "NX" end
+love.filesystem.getSaveDirectory = function() return "/save/pokemon-love2d" end
+
+package.loaded["src.core.Platform"] = nil
+package.loaded["src.import.RomImporter"] = nil
+local RomImporter = require("src.import.RomImporter")
+
+local ri = RomImporter.new(function() end, { launcher = true })
+ri.ready = { red = false, blue = false, yellow = false }
+
+popenCalls = 0
+ri:choose("red")
+eq(popenCalls, 0, "choose on NX does not call HostShell.popen")
+check(ri.notice ~= nil, "NX choose sets a save-directory notice")
+check(ri.notice.detail:find("imports", 1, true) ~= nil,
+  "notice mentions imports inbox path")
+
+-- Desktop path still reaches the shell when a picker exists.
+love.system.getOS = function() return "Linux" end
+package.loaded["src.core.Platform"] = nil
+package.loaded["src.import.RomImporter"] = nil
+RomImporter = require("src.import.RomImporter")
+ri = RomImporter.new(function() end, { launcher = true })
+ri.ready = { red = false, blue = false, yellow = false }
+popenCalls = 0
+ri:choose("red")
+check(popenCalls >= 1 or ri.notice ~= nil,
+  "Linux choose still attempts shell picker or falls back with notice")
+
+package.loaded["src.core.HostShell"] = realHostShell
+package.loaded["src.core.Platform"] = nil
+package.loaded["src.import.RomImporter"] = nil
+
+S.finish()

tests/run_tests.lua

@@ -3371,6 +3371,7 @@ 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" })
+runSuites({ "tests/platform_nx_shell_gate_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