Add full compiler toolchain, libc, examples and reference docs

First substantive commit: the entire Sprinter C compiler tree on top of
the bare README+gitignore initial commit.

What's in here:
  bin/sprinter-cc        — driver script invoking SDCC + linker + mkexe
  libc/                  — Sprinter-specific libc layer over ESTEX/BIOS
                           (conio, gfx, io, mem, stdio + headers)
  runtime/               — crt0 variants (default/small/banked/minimal)
                           + heap + bank trampolines
  toolchain/             — mkexe (SprintEXE packer, C + tests)
  examples/              — 30 demo programs (gfx, file I/O, env, time, …)
  lib/Makefile           — builds the libc archive (sprinter.lib)
  docs/                  — converted Sprinter manuals + asm reference samples
  third_party/           — solid-c reference compiler dump + sdcc setup script
  release_docs/          — packaging / release notes

gitignore overhaul:
  • Drop dangerous blanket patterns: *.asm (would hide docs/samples/*.asm)
    and *.exe (case-insensitive match was hiding third_party/solid-c/*.EXE
    on macOS APFS).  Replaced with examples/*/*.{asm,exe,…} and lib/*.lib.
  • Restore tracking of toolchain/mkexe/tests/{one,big}.bin — those are
    INPUT fixtures, not build outputs.
  • Collapse the duplicated SDCC/C/Sdcc sections into one section per
    concern (build outputs / vendored / OS-junk).
  • Add .sprinter-cc-*/, build/ (catches lib/build/ too), .claude/.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

third_party/solid-c/EXAMPLES/FEOF.C

@@ -0,0 +1,28 @@
+               FEOF
+            
+#include <stdio.h>               ¤«ï ®¡ê¥­¨ï ä㭪樨
+int feof(FILE *fp);
+            
+  ”ã­ªæ¨ï (ॠ«¨§®¢ ­­ ï ª ª ¬ ªà®) ®¯à¥¤¥«ï¥â, ¤®á⨣­ãâ «¨ ª®­¥æ § ¤ ­-
+­®£® ä ©« . …᫨ ª®­¥æ ä ©«  (EOF) ¤®á⨣­ãâ, â® áâ ­®¢ïâáï ­¥¤®áâ㯭묨
+®¯¥à æ¨¨ ç⥭¨ï, â.¥. ¯à¨ ª ¦¤®© ®¯¥à æ¨¨ ç⥭¨ï, ¡ã¤¥â ¢®§¢à é âìáï ¯à¨§-
+­ ª ª®­æ  ä ©« , ¯®ª  ä ©« ­¥ ¡ã¤¥â § ªàëâ ¨«¨ ¢ë§¢ ­ë ä㭪樨 rewind,
+fsetpos, fseek ¨«¨ clearerr.
+…᫨ ⥪ãé ï ¯®§¨æ¨ï ï¥âáï ª®­æ®¬ ä ©«  (EOF), äã­ªæ¨ï ¢®§¢à é ¥â ­¥­ã-
+«¥¢®¥ §­ ç¥­¨¥. …᫨ ⥪ãé ï ¯®§¨æ¨ï ­¥ ï¥âáï ª®­æ®¬ ä ©«  - ¢®§¢à é -
+¥âáï §­ ç¥­¨¥ 0. ”ã­ªæ¨ï feof ®è¨¡®ª ­¥ ¢®§¢à é ¥â.
+
+#include <stdio.h>
+FILE *fp;
+main()
+{
+   if((fp=fopen("file.dat", "r")) == NULL)
+     {
+       printf("Žè¨¡ª  ®âªàëâ¨ï ä ©« \n");
+       exit(1);
+     }
+   while(!feof(fp))
+       fgetc(fp);
+   printf("\n” ©« ¯à®ç¨â ­, ¢áâà¥â¨«áï EOF\n");
+   fclose(fp);
+}