VSH: An empty UMD drive, and inserting a disc over the WebSocket debugger

The XMB, booted without a game, now starts with an empty drive: when
vsh_module loads with nothing at disc0:, the drive is marked empty, and
activating it tells the shell's drive callback (SceVshMediaDetectUMD)
there's no disc. Activation used to report a readable disc regardless,
so the shell asked for its type and showed "The disc could not be read."
The disc type devctl (0x01F20001) answers 0 without a disc, as JPCSP
does.

game.umd.insert (path) mounts a disc image into the empty drive and
calls the drive callback as inserting one does; game.umd.eject takes it
out. UmdMount() is UmdReplace() without its need for a disc already in.

Inserted into the 6.61 XMB, Daxter shows in the Game column with its
icon, background and animated preview, and launching it boots the game
to its title menu.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/WebSocketDebugger.md

@@ -271,7 +271,7 @@ file - this is just an index.
 
 | Category | Events | File |
 |---|---|---|
-| Game/version | `game.reset`, `game.status`, `game.state.load` (queue loading a `.ppst` file given as `path`, or a `slot` of the running game, applied at the end of the next frame the CPU runs; with `wait: true` the response comes once it's done, or as an error if it failed), `game.state.save` (the same for saving one), `game.state.rewind` (the same for the newest rewind snapshot, which it keeps, so only a rewind within 0.8 seconds of the last steps further back; needs `RewindSnapshotInterval` set, and the `wait` response's `metadata` says how far back that is in emulated time), `game.state.verify` (the same for checking that saving the current state and reading it back agree), `game.speed.get/set` (emulation speed - unlimited fast-forward, or a percentage of 60 FPS; see below), `version` | `GameSubscriber.cpp` |
+| Game/version | `game.reset`, `game.status`, `game.state.load` (queue loading a `.ppst` file given as `path`, or a `slot` of the running game, applied at the end of the next frame the CPU runs; with `wait: true` the response comes once it's done, or as an error if it failed), `game.state.save` (the same for saving one), `game.state.rewind` (the same for the newest rewind snapshot, which it keeps, so only a rewind within 0.8 seconds of the last steps further back; needs `RewindSnapshotInterval` set, and the `wait` response's `metadata` says how far back that is in emulated time), `game.state.verify` (the same for checking that saving the current state and reading it back agree), `game.speed.get/set` (emulation speed - unlimited fast-forward, or a percentage of 60 FPS; see below), `game.umd.insert` / `game.umd.eject` (put a disc image, given as `path`, in an empty drive, or take it out: for the XMB booted with `--vsh` and no game, which then lists the disc and can launch it), `version` | `GameSubscriber.cpp` |
 | CPU core | `cpu.stepping`, `cpu.resume`, `cpu.status` (reports `ticks` plus `us`, emulated microseconds, and `clockHz` - use `us` to line up with wall-clock timings, since games change the clock frequency and the ticks-per-second ratio isn't fixed), `cpu.getAllRegs`, `cpu.getReg`, `cpu.setReg`, `cpu.evaluate` | `CPUCoreSubscriber.cpp` |
 | Stepping | `cpu.stepInto`, `cpu.stepOver`, `cpu.stepOut`, `cpu.runUntil`, `cpu.runUntilTime` (run until a point in emulated time - `us` absolute or `relativeUs` from now - and break there; this is how to get a scripted repro reproducibly "N seconds into the game" instead of polling `cpu.status` in a loop), `cpu.nextHLE` | `SteppingSubscriber.cpp` |
 | Breakpoints | `cpu.breakpoint.add/update/remove/list`, `memory.breakpoint.add/update/remove/list`, `cpu.regBreakpoint.add/update/remove/list` (break when a register is written to, by any instruction anywhere - currently GPRs only; interpreter-only, no effect under a JIT backend) | `BreakpointSubscriber.cpp` |