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>

examples/ls/Makefile

@@ -0,0 +1,5 @@
+# Build ls.exe — uses lib/sprinter.lib in TINY memory mode.
+
+PROJ_ROOT := $(abspath $(CURDIR)/../..)
+EXAMPLE   := ls
+include $(PROJ_ROOT)/examples/example.mk

examples/ls/ls.c

@@ -0,0 +1,96 @@
+#include <stdio.h>
+#include <string.h>
+#include <conio.h>
+#include <dir.h>
+#include <errno.h>
+
+/*
+ * ls — list files on the current drive that match the given pattern.
+ *
+ *     LS                  -> "*.*" (everything in current dir)
+ *     LS *.TXT            -> just .TXT files
+ *     LS C:               -> auto-rewritten to "C:*.*"
+ *     LS C:\BIN           -> "C:\BIN\*.*"
+ *     LS C:\BIN\          -> "C:\BIN\*.*"
+ *     LS /A               -> include hidden / system / label entries
+ *
+ * ESTEX F_FIRST itself returns errno 16 (EINAME) when given a bare path
+ * with no wildcard, so we patch the pattern up before calling it.
+ */
+
+/*
+ * Sprinter ESTEX F_FIRST refuses bare path components — it needs a real
+ * wildcard.  We do the minimum that DOS-style shells do for the user:
+ *   - "C:"    →  "C:\*.*"    (drive without slash)
+ *   - "C:\"   →  "C:\*.*"    (root-like, just append the wildcard)
+ *   - anything else: pass through.  A more correct implementation would
+ *     stat the path and decide between "single file" / "directory" — out
+ *     of scope for this example.
+ */
+static char *normalize_pattern(const char *src, char *dst, int cap)
+{
+    int len = (int)strlen(src);
+    if (len == 0) {
+        strcpy(dst, "*.*");
+        return dst;
+    }
+
+    char last = src[len - 1];
+    const char *suffix = NULL;
+    if      (last == ':')                          suffix = "\\*.*";
+    else if (last == '\\' || last == '/')          suffix = "*.*";
+
+    if (suffix && len + (int)strlen(suffix) + 1 <= cap) {
+        strcpy(dst, src);
+        strcat(dst, suffix);
+    } else {
+        strcpy(dst, src);
+    }
+    return dst;
+}
+
+int main(int argc, char **argv)
+{
+    const char *pattern_in = "*.*";
+    uint8_t     attr       = FA_NORMAL | FA_DIREC | FA_RDONLY | FA_ARCH;
+
+    for (int i = 1; i < argc; i++) {
+        if (argv[i][0] == '/' && (argv[i][1] | 0x20) == 'a') {
+            attr |= FA_HIDDEN | FA_SYSTEM | FA_LABEL;
+        } else {
+            pattern_in = argv[i];
+        }
+    }
+
+    char pattern[80];
+    normalize_pattern(pattern_in, pattern, sizeof(pattern));
+
+    printf("ls: pattern=\"%s\" attr=0x%02X\n\n", pattern, attr);
+
+    ffblk_t blk;
+    int r = ffirst(pattern, &blk, attr);
+    if (r < 0) {
+        printf("no match (errno=%d %s)\n", errno, strerror(errno));
+        cputs("\nPress any key to exit.\n");
+        (void)getch();
+        return 1;
+    }
+
+    int count = 0;
+    do {
+        const char *kind;
+        if      (blk.found_attr & FA_DIREC)  kind = "<DIR>";
+        else if (blk.found_attr & FA_LABEL)  kind = "<VOL>";
+        else if (blk.found_attr & FA_SYSTEM) kind = "[SYS]";
+        else if (blk.found_attr & FA_HIDDEN) kind = "[HID]";
+        else                                  kind = "     ";
+
+        printf("  %s  %-14s %8lu\n", kind, blk.found_name, blk.size);
+        count++;
+    } while (fnext(&blk) == 0);
+
+    printf("\n%d entries\n\n", count);
+    cputs("Press any key to exit.\n");
+    (void)getch();
+    return 0;
+}