fix: point VMCDIR.TXT at disc 1's folder, not its VCD file

[casmith]

A multi-disc game would have lost the player's save at the disc change.

VMCDIR.TXT names the support directory whose memory card a disc shares. ps2hdd wrote the VCD's filename into it:

SLUS_005.94.Metal Gear Solid_CD1.VCD    was written
SLUS_005.94.Metal Gear Solid_CD1        is correct

Four characters, and it fails silently. POPStarter finds no folder of that name, falls back to giving the disc a virtual memory card of its own, and a save made on disc 1 is simply not there on disc 2.

That is precisely the failure the comment on writePS1Support describes and says must not happen:

a three-disc RPG that loses your save at the disc change is technically installed and practically useless

Found while answering a question about how disc swapping works, by reading POPStarter's documented file formats instead of assuming ours matched them.

Two more limits from the same source, both silent

Filename length. A VCD name has to fit the buffer DISCS.TXT paths are read into, which caps it at roughly 73 characters — not the 89 POPStarter's wiki quotes. maxVCDNameLen drops to 73 for every title: a name is only an identifier, and a shorter one costs nothing next to a multi-disc game that cannot change discs.

Disc count. DISCS.TXT describes at most four discs. A title with more installs and boots exactly as before, and now says its disc-swap menu will not work rather than leaving that to be discovered mid-game.

The tests encoded the bug

All three of them — the unit test, the app-level test, and scripts/demo-smoke.sh — asserted _CD1.VCD in VMCDIR.TXT. They now assert the documented format, and explicitly that the file carries no .VCD extension, along with POPStarter's 103-byte and no-path-separator limits.

Mutation-checked: restoring the old one-line contents compiles and fails both the unit test and the app test.

New coverage:

• TestVCDNameFitsTheDiscsFileBuffer — names stay inside the buffer at every disc number, and the _CDn suffix survives truncation, since a title cut back to a shared prefix would install four files under one name.
• TestDiscsFileListsFilenames — every line names a .VCD (unlike VMCDIR.TXT), lines are in disc order, and each fits the buffer.

Full suite, go vet, gofmt and the smoke test pass.

Source: POPStarter Docs — Multi-disc & VMC

https://claude.ai/code/session_018eBAB3V9GRxNwgpQcpGje4