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>

libc/stdio/puts.c

@@ -0,0 +1,69 @@
+/*
+ * puts — C99 fputs(s, stdout) + '\n'.
+ *
+ * Turbo-C convention: stdio's `puts` is the FAST path with NO attribute
+ * control — backed by ESTEX PCHARS ($5C).  Cursor cell attributes are
+ * whatever ESTEX has cached (usually the shell's default).
+ *
+ * For coloured output use cputs() / cprintf() from <conio.h>.
+ *
+ * Implementation notes:
+ *   - PCHARS does NOT translate '\n' to CR LF, so we copy the string
+ *     into a static buffer expanding each '\n' to CR LF, then append
+ *     the trailing CR LF before the NUL.
+ *   - Avoid trailing PUTCHAR after PCHARS — empirically that sometimes
+ *     drops the next char.  Embed the line ending inside the PCHARS
+ *     buffer instead.
+ *   - Strings longer than the buffer fall back to per-char putchar so
+ *     we never silently truncate.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+
+#define PUTS_BUF_SIZE  256       /* body bytes before CR expansion */
+
+static char puts_buf[PUTS_BUF_SIZE + 3];   /* +3 for trailing CR LF NUL */
+
+static void pchars(const char *s) __naked
+{
+    (void)s;
+    __asm
+        push  ix
+        ld    c, #0x5C
+        rst   #0x10
+        pop   ix
+        ret
+    __endasm;
+}
+
+int puts(const char *s)
+{
+    uint16_t n = 0;
+    uint16_t i = 0;
+
+    while (s[i] && n < PUTS_BUF_SIZE - 1) {
+        char c = s[i++];
+        if (c == '\n') {
+            puts_buf[n++] = '\r';
+            puts_buf[n++] = '\n';
+        } else {
+            puts_buf[n++] = c;
+        }
+    }
+
+    if (s[i]) {
+        /* Overflow — char-by-char fallback so we never truncate. */
+        for (uint16_t k = 0; s[k]; k++)
+            putchar((unsigned char)s[k]);
+        putchar('\n');
+        return 0;
+    }
+
+    puts_buf[n++] = '\r';
+    puts_buf[n++] = '\n';
+    puts_buf[n]   = 0;
+
+    pchars(puts_buf);
+    return 0;
+}