lib: char-literals for ascii/fnmatch/shlex magic decimals (Wave-1)

Replace magic ASCII decimals with char literals in ascii/fnmatch/shlex
predicates (e.g. `c < 48` → `c < '0'`). Byte-id-neutral: ascii params are
rune, so rune<rune emission is unchanged; fnmatch/shlex compare u8 against
value-preserving (<=126) rune constants. Range bounds (0/31/127), the ±32
case offset, the 128 high-bit mask, and fnmatch 0u8 sentinels stay decimal.

Regenerate the three combined.ww that embed ascii (w6c, wwdump, smoke).

Add functional rows pinning predicates reachable only via fnmatch ctype
classes / shlex split: [[:space:]]/[[:print:]]/[[:graph:]] + the '\t' arm
of [[:blank:]] (fnmatchtest), '\t'/'\n' split separators + issafe's
special-char set (shlextest) — so a wrong substitution would be caught.

lib/shlex/shlextest.ww

@@ -149,6 +149,8 @@ fn checkquote(in: str, expected: str) void = {
 	check3("with\\ backslashes 'single quoted' \"double quoted\"",
 	    "with backslashes", "single quoted", "double quoted");
 	check2("'multiple spaces'      42", "multiple spaces", "42");
+	// pin the '\t'/'\n' arms of split's whitespace test.
+	check3("a\tb\nc", "a", "b", "c");
 
 	// Invalid
 	checkerr("\"dangling double quote");
@@ -172,6 +174,8 @@ fn checkquote(in: str, expected: str) void = {
 	checkquote("'hello' \"world\"", "''\"'\"'hello'\"'\"' \"world\"'");
 	checkquote("hello\\world", "'hello\\world'");
 	checkquote("", "''");
+	// pin issafe's special-char set: all safe → emitted raw, unquoted.
+	checkquote("@%+=:,./-", "@%+=:,./-");
 };
 
 // ---- quotestr ------------------------------------------------------