Fix Mii Maker image export feature

[ariankordi]

This PR gets rid of the "please insert an SD card" error that previously showed up if you tried to use this feature, so that it now works and is fully preserved (like it is in Citra).


Mii QR codes can also export now, albehit the data is all zeroes because Mii encryption is unimplemented:

Changes made

• 345ba08: Invoke SD card callback/notification when FSAddClientEx is called.
  • If Mii Maker never receives this, it doesn't even try to mount the SD card despite it being present.
  • The workaround I applied is to invoke the callback immediately with the string "sdcard".
    • It’s possible this affects other games that use the SD card, if… there are any.
  • That FSAttachCallback is slightly documented in Decaf.
• 1e1b2c1: Fix image texture readback in Mii Maker
  • As you can see, I had to remove an assertion that got hit while doing this. Context is needed on why it was originally added.
  • Also had to enable TM_LINEAR_GENERAL to be mirrored to CPU RAM as well as TM_LINEAR_ALIGNED.
  • Even with these changes, JPEGs for QR codes are still completely black under the Metal renderer while Vulkan is fine.
• 244aeb0: Extra change I snuck in to export FSRewindDir.
  • Already implemented, called by "FFLUtility". (Search in RGD Discord for more info)
    • According to the paths, it's built from the same sources as Mii Maker. So yes, Mii
  • This patch and a mount at /fflutility will make the tool work (--cos-mounts /path/to/hostio:/fflutility)
    • Weirdly not required on a real console.
  • DM me if you'd like to test this.

Fixing QR codes

Proper QR code exports involve implementing ACPMiiWrap/Unwrap, which I could do, but is out of scope and well documented anyway.

• Used for Mii QR code encryption yes, but also for some obscure Mii network features.
  • sonic2013.rpx: WrapStoreData__31__N_15_FFLiNetwork_cpp_5a76681bFP20FFLiWrappedStoreDataPC16FFLiStoreDataCFLb
• The concern here is with the AES key it needs, which Citra uses from the txt.
  • Not my call if it should be included in the code, but does Cemu even require keys anywhere else?
  • Citra actually uses 0 as the key if unspecified. Those null-key QR codes, while mostly useless, CAN actually be read/created by a tool I made.
• Or we can defer this to until camera support works. Then the entire feature can be tested end-to-end.

[Exzap]

Appreciate the contribution, but our LLM policy requires all code to be written by a human. You can find the full policy and reasons in README.md

[ariankordi]

Sorry about that, the SD change was from Claude with rewritten comments. I reverted and redid that one by hand.