Cover required imports across platforms

docs/launcher.md

@@ -16,6 +16,7 @@ save directory as:
 | nil / `"rom"` | `picked_rom.gb` (open) |
 | `"mod"` | `picked_mod.zip` (open) |
 | `"sav"` / `"save"` | `picked_save.sav` (open) |
+| `"required_import"` | `picked_required_import.bin` (open) |
 
 Export uses a separate API: `love.system.createFile(suggestedName)` →
 `GameActivity.showCreateDocument` (`ACTION_CREATE_DOCUMENT`), which copies

docs/modding.md

@@ -148,6 +148,18 @@ older iOS-only `"stadium"` picker kind remains temporarily for compatibility.
 Android now returns `false` for unknown picker kinds instead of treating them
 as game-ROM picks.
 
+### Platform import flow
+
+The same per-mod validation and private `mods/<mod-id>/baseroms/` destination
+applies on every supported platform. Windows, macOS, and Linux use the
+launcher file chooser. Android uses the Storage Access Framework, and iOS uses
+the Files document picker; both stage the choice as `picked_required_import.bin`
+before validation. Xbox/UWP uses its native picker and hands the launcher a
+temporary path. Switch/NX has no host picker, so the player copies a file to
+`imports/baseroms/` over MTP and chooses the import again. No platform grants
+the mod a host filesystem path or bypasses the manifest's size, format, and MD5
+checks.
+
 ## Mods and Gold (Gen 2)
 
 The mod API is one API across both generations, but Gold runs its own battle