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/INCLUDE/STDLIB.H

@@ -0,0 +1,51 @@
+/*
+ *	STDLIB.H
+ *
+ *	A header for a standart library CLIB.
+ *	(c) 2004, SOLID C  Sprinter-2000
+ */
+
+
+#ifndef	_C_TYPES_
+#include <types.h>
+#endif
+
+#ifndef	_STD_LIB_
+#define	_STD_LIB_
+
+char errno;			/* must be declaration here */
+
+
+/* for "div" function */
+typedef struct divt {
+        uint	quot;		/* ç áâ­®¥ */
+        uint	rem;		/* ®áâ â®ª */
+} div_t;
+
+
+int abs();
+int atoi();
+int min();
+int max();
+int strtol();
+int rand();
+void *bsearch();
+void qsort();
+void srand();
+void perror();
+void exit();
+void _exit();
+void abort();
+char atexit();
+char *sysenv();
+char *getenv();
+uint putenv();
+struct divt *div();
+void hex8();
+void hex16();
+void hex32();
+void dec8();
+void dec16();
+void dec32();
+
+#endif