feature: mirror all diagnostics to syslog, add VESA fallback for gfxd crashes

- syslogDump now outputs all five diagnostic sections (Fault Info,
  CPU Registers, Process Info, System Info, Call Stack) to serial,
  matching the on-screen BSOD content
- panic() detects if the crash occurred in the gfxd process and
  falls back to rendering the BSOD directly to the VESA framebuffer
  via driver.video text drawing, bypassing LVGL entirely
- Add DrawChar, DrawString, DrawHex, DrawInt to driver.video for
  8x16 bitmap font rendering directly to the framebuffer
- Export SHOULD_CRASH flag from svc.gfxd interface so test commands
  can trigger a deliberate gfxd crash
- Add app.divzero with DIV0, PF, and CRASHGFXD test commands
- Update doc/src/core/core.panic.md and doc/src/driver/video/driver.video.md

src/app/app.divzero.pas

@@ -0,0 +1,57 @@
+{
+    Prog->Ping - ICMP Ping command.
+
+    Sends 10 ICMP echo requests to a host, printing round-trip time
+    for each reply. Sleeps 1 second between pings. Each invocation
+    uses a heap-allocated state record so multiple terminals can app.ping
+    concurrently without corrupting each other.
+
+    @author(Kieron Morris <[email protected]>)
+}
+unit app.divzero;
+
+interface
+
+uses
+    io.stdio, debug.tracer;
+
+procedure init();
+
+implementation
+
+uses
+    arch.x86.bda, driver.net.types, driver.net.proto.icmp, driver.net.util, core.strings,
+    proc.mgr, core.util, arch.x86.util, memory.heap, svc.gfxd;
+
+{ ---- Command entry point (runs as a process) ---- }
+
+procedure run_div0(Params : PParamList; stdin_buf, stdout_buf, stderr_buf : POutBuf);
+begin
+    asm
+        XOR EAX, EAX
+        DIV EAX  { this will trigger a divide by zero exception (interrupt 0) }
+    end;
+end;
+
+procedure run_pf(Params : PParamList; stdin_buf, stdout_buf, stderr_buf : POutBuf);
+begin
+    asm
+        MOV EAX, $DEADBEEF
+        MOV [EAX], EAX  { this will trigger a page fault (interrupt 14) }
+    end;
+end;
+
+procedure run_div0_gfxd(Params : PParamList; stdin_buf, stdout_buf, stderr_buf : POutBuf);
+begin
+    svc.gfxd.SHOULD_CRASH := true;  { set flag to trigger crash in graphics service }
+end;
+
+procedure init();
+begin
+    debug.tracer.push_trace('divzero.init');
+    io.stdio.registerCommand('DIV0', @run_div0, 'Force a divide by zero exception.');
+    io.stdio.registerCommand('PF', @run_pf, 'Force a page fault.');
+    io.stdio.registerCommand('CRASHGFXD', @run_div0_gfxd, 'Force a divide by zero exception in the graphics service.');
+end;
+
+end.

src/app/app.mgr.pas

@@ -33,7 +33,8 @@ uses
     //dispatch
     driver.storage.filedispatch,
     //wasm
-    app.wasm.runner;
+    app.wasm.runner,
+    app.divzero;
 
 { Initialize all baked-in programs }
 procedure init();
@@ -81,6 +82,7 @@ begin
     driver.storage.filedispatch.init();
     app.wasm.runner.init();
     app.setres.init();
+    app.divzero.init();
 end;
 
 end.