lib: rename stdlib surface to Hare names; add endian/math

Sweeping rename so the lib/ surface mirrors Hare's stdlib spellings.
- ascii: rune-taking predicates; ishex -> isxdigit
- bufio: rinit -> init; take1/takeline -> readbyte/readline
- bytes: indexsub -> index
- encoding/utf8: runelen -> runesz
- errors: eEOF/eShortRead/... -> eof/underread/...
- fmt: errln -> errorln; println/fprintln return i64
- os: readfull/writefull -> readall/writeall; unlink -> remove
- path: isabs -> abs; drop lastindex (now strings.rbyteindex)
- strconv: u64toa/i64toa -> u64tos/i64tos; parse64/parseu64 -> stoi64/stou64
- strings: drop len/isempty; equal -> compare; indexbyte -> byteindex; +rbyteindex
- types: drop numeric helpers (moved to math)
- new lib/endian (htonu16/ntohu16), lib/math (absi32/absi64)
- net: drop htons (use endian.htonu16)

Callers in selfhost/, lib/ww/, cmd/w6c/cgen.c, and test/wcc/700_e2e.c
updated to match.

lib/strings/strings.ww

@@ -1,23 +1,21 @@
 // strings — operations over the immutable str type ({ *u8, len }).
+// Mirrors Hare's strings::; `len` and `is-empty` aren't functions
+// (callers use `s.len` and `s.len == 0` directly).
 
 use os;
 
-export fn len(s: str) i32 = {
-	return s.len;
-};
-
-export fn isempty(s: str) bool = {
-	return s.len == 0;
-};
-
-export fn equal(a: str, b: str) bool = {
-	if (a.len != b.len) { return false; };
+// compare — bytewise three-way comparison: negative if a<b, 0 if equal,
+// positive if a>b. Matches Hare's strings::compare. ASCII-order, not
+// locale-aware. Callers that just need equality use `compare(a, b) == 0`.
+export fn compare(a: str, b: str) i32 = {
+	let n: i32 = a.len;
+	if (b.len < n) { n = b.len; };
 	let i: i32 = 0;
-	for (i < a.len) {
-		if (a[i] != b[i]) { return false; };
+	for (i < n) {
+		if (a[i] != b[i]) { return (a[i]: i32) - (b[i]: i32); };
 		i += 1;
 	};
-	return true;
+	return a.len - b.len;
 };
 
 export fn hasprefix(s: str, p: str) bool = {
@@ -41,10 +39,11 @@ export fn hassuffix(s: str, suf: str) bool = {
 	return true;
 };
 
-// indexbyte — first index of `c` in `s`, or -1 if absent. Plan 9-
-// style sentinel return; callers that prefer a fallible shape can
-// wrap this in their own (i32 | str). No allocation.
-export fn indexbyte(s: str, c: u8) i32 = {
+// byteindex — first index of byte `c` in `s`, or -1 if absent. Hare
+// name (strings::byteindex). Plan 9-style sentinel return; callers that
+// prefer a fallible shape can wrap this in their own (i32 | str). No
+// allocation.
+export fn byteindex(s: str, c: u8) i32 = {
 	let i: i32 = 0;
 	for (i < s.len) {
 		if (s[i] == c) { return i; };
@@ -53,6 +52,17 @@ export fn indexbyte(s: str, c: u8) i32 = {
 	return -1;
 };
 
+// rbyteindex — last index of byte `c` in `s`, or -1 if absent. Mirrors
+// Hare's strings::rbyteindex.
+export fn rbyteindex(s: str, c: u8) i32 = {
+	let i: i32 = s.len - 1;
+	for (i >= 0) {
+		if (s[i] == c) { return i; };
+		i -= 1;
+	};
+	return -1;
+};
+
 // index — first index of `sub` in `s`, or -1. Naive scan; fine for
 // short patterns and small strings, which dominate config and CLI
 // parsing. Empty `sub` matches at 0.