Merge pull request #1616 from HighDrexler/fix/large-required-imports-v2

Fix/large required imports v2

docs/modding.md

@@ -122,21 +122,40 @@ Each object requires a stable `id`, a display `name`, a destination `file`
 digests. `format` is either `"raw"` (the default) or `"n64"`. An optional
 `description` gives players dump or region guidance in the import panel.
 `size` declares the exact canonical byte length; `max_size` declares a smaller
-per-import ceiling when an exact size is not appropriate. Every import also
-has an engine-enforced 128 MiB ceiling and is rejected before hashing when its
-filesystem reports an invalid size.
+per-import ceiling when an exact size is not appropriate. The engine hard limit
+is 2 GiB. Imports above 128 MiB receive an explicit free-space confirmation and
+use the launcher's streaming large-file path rather than being materialized as
+one Lua string.
 
 For `"n64"`, the launcher recognizes `.z64`, `.v64`, and `.n64` byte orders,
 strips a recognized 512-byte copier header, converts the bytes to canonical
 big-endian `.z64` order, and then checks MD5. The canonical bytes are written
 to `mods/<mod-id>/baseroms/<file>`. Each selection is a private grant to that
 mod: the launcher never scans or copies another mod's imported files merely
-because its manifest names the same digest. Mods read the result with their existing scoped `mod:read` API, for
-example `mod:read("baseroms/stadium2.z64")`; no host path or new filesystem
+because its manifest names the same digest. Small sources can still be read
+with the existing scoped `mod:read` API, for example
+`mod:read("baseroms/stadium2.z64")`. For large sources, prefer the bounded
+`mod.imports` facade described below; no host path or new general filesystem
 permission is exposed. Missing `required_imports` block the mod before its
 entry chunk runs; missing `optional_imports` remain visible in the same
 launcher panel but do not block loading.
 
+#### Bounded access to validated imports
+
+A loaded mod can address only ids declared by its own `required_imports` or
+`optional_imports` arrays:
+
+```lua
+local info, err = mod.imports:info("stadium2")
+local header, err = mod.imports:read("stadium2", 0, 4096)
+```
+
+`read` uses zero-based offsets and is capped at 8 MiB per call. The engine
+rechecks the stored import before exposing it, seeks into the engine-owned
+copy, and never gives the mod a host path or file handle. This is intended for
+large source formats whose table/index can be parsed with small reads before
+selectively reading the payloads a transform actually needs.
+
 MD5 here identifies a known dump because ROM databases commonly publish it;
 it is not a security or authenticity guarantee. Do not paste the SHA-1 used by
 Gen1Recomp's own game-ROM importer into an import's `md5` field. Mod archives
@@ -441,6 +460,28 @@ default** (1x front, 2x back).
   ball-to-pic grow multiplies your scale through each stage, so a rescaled
   mon still grows into place from the ball, grounded the whole way.
 
+## Installation-scoped generated cache
+
+Generated data derived from a validated user source often belongs to the mod
+installation rather than to one Pokémon save. `mod.cache` is that namespace:
+
+```lua
+local ok, err = mod.cache:write("extract/v1/arena.bin", encodedArena)
+local bytes, err = mod.cache:read("extract/v1/arena.bin")
+local info = mod.cache:info("extract/v1/arena.bin")
+mod.cache:delete("extract/v1/arena.bin")
+```
+
+The physical root is engine-owned (`mod_cache/<mod-id>/`) and never exposed to
+the mod. Keys are safe relative paths and a single write is capped at 64 MiB.
+The cache does not rewind with checkpoints and is not scoped to game version,
+slot, or playthrough. The mod owns its generated format, fingerprints, rebuild
+policy, and completion marker; the engine treats the bytes as opaque data.
+
+Use `mod.storage` instead when the data belongs to one playthrough. Use
+`mod.cache` when it is a reproducible installation artifact that can be rebuilt
+from a declared user source.
+
 ## Durable tool storage and runtime checkpoints
 
 `mod.save` remains the right place for state that should travel with the next