WebSocket debugger: Any savestate slot in headless

game.state.save and game.state.load with a slot were limited to the
app's slot count (5 by default), which only means how many the UI shows.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Core/Debugger/WebSocket/GameSubscriber.cpp

@@ -115,7 +115,8 @@ void WebSocketGameState::StateOperation(DebuggerRequest &req, StateOp op) {
 	if (useSlot) {
 		if (!req.ParamU32("slot", &slot))
 			return;
-		if (slot >= (uint32_t)g_Config.iSaveStateSlotCount)
+		// The slot count is how many the app's UI shows. Headless has no UI to show them in.
+		if (slot >= (uint32_t)g_Config.iSaveStateSlotCount && !System_GetPropertyBool(SYSPROP_IS_HEADLESS))
 			return req.Fail("Invalid slot");
 	} else if ((op == StateOp::LOAD || op == StateOp::SAVE) && !req.ParamString("path", &path)) {
 		return;

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; all but this one are refused in a session booted into the XMB, whose discs come and go), `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` |
+| Game/version | `game.reset`, `game.status`, `game.state.load` (queue loading a `.ppst` file given as `path`, or a `slot` of the running game (any slot in headless, otherwise one the app's slot count shows), 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; all but this one are refused in a session booted into the XMB, whose discs come and go), `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` |