lib/ww/lex + selfhost/cmd: astrndup → strings.dup view (γ-1)

#7 Phase A first cut. 13 of 15 astrndup callers converted to the
explicit (*u8, n) → str view + strings.dup shape (ref/hare/strings/
dup.ha:7). astrndup export stays in selfhost/cmd/wcc/mem.ww — 2 w6a
sites blocked by the selfhost/cmd/w6a/types.ww shadow (filed as #11)
and carry an inline WHY pointer until the rename ships.

NUL-dependence audit: no consumer reads token text past `.len`. tok.text
flows through fputq (length-bounded) and parse.curtext → n.str (streq-
based dispatch across check/cgenutil); p.file is written via os.write
(ptr,len); selfhost/cmd/ww/main.ww's astrndup'd pathstr only flows into
visitseen/visitadd's manual byte-loop, while all OS calls in that file
use the unrelated `pathstr(*u8) str` view helper on the raw pointer.

Empty-str sites (lex.ww:579, 624, 640) collapse to strings.dup of an
empty view; strings.dup short-circuits len==0 (lib/strings/strings.ww:72)
and returns {nil, 0} — observationally identical to astrndup's prior
{arena_1byte, 0}.

Sites:
 - lib/ww/lex/lex.ww (8: 450, 529, 554, 564, 579, 624, 640, 794)
 - selfhost/cmd/w6c/main.ww:139
 - selfhost/cmd/w6l/dyn.ww:111 (inside dcstrtostr)
 - selfhost/cmd/w6l/obj.ww:185 (inside cstrtostr)
 - selfhost/cmd/ww/main.ww:531

Wrappers (dupstr/cstrtostr/dcstrtostr) keep their bodies; deletion
deferred to #10.

selfhost/cmd/wwdump/main.combined.ww

@@ -3730,6 +3730,7 @@ package lex;
 import os;
 import ascii;
 import mem;
+import strings;
 
 // isidstart / isidpart — identifier classification. Lexer-local
 // because the "alpha or '_' / alnum or '_'" set isn't part of Hare's
@@ -4159,7 +4160,10 @@ fn lexnum(l: *lex, start: *pos, out: *tok) void = {
 	};
 
 	let n: u64 = l.lpos - begin;
-	out.text = astrndup(l.a, l.src + begin, n);
+	let view: str;
+	view.ptr = l.src + begin;
+	view.len = n: i32;
+	out.text = strings.dup(view);
 
 	if (isfloat) {
 		out.kind = tkind.TK_FLOAT;
@@ -4238,7 +4242,10 @@ fn lexnum(l: *lex, start: *pos, out: *tok) void = {
 				};
 			};
 			if (isok) {
-				out.tsuffix = astrndup(l.a, p, sl);
+				let view: str;
+				view.ptr = p;
+				view.len = sl: i32;
+				out.tsuffix = strings.dup(view);
 			} else {
 				l.lpos = sb;
 			};
@@ -4263,7 +4270,10 @@ fn lexident(l: *lex, start: *pos, out: *tok) void = {
 	if (n == 1u64) {
 		if (p[0] == 95u8) {
 			out.kind = tkind.TK_UNDER;
-			out.text = astrndup(l.a, p, n);
+			let view: str;
+			view.ptr = p;
+			view.len = n: i32;
+			out.text = strings.dup(view);
 			return;
 		};
 	};
@@ -4273,7 +4283,10 @@ fn lexident(l: *lex, start: *pos, out: *tok) void = {
 	} else {
 		out.kind = tkind.TK_IDENT;
 	};
-	out.text = astrndup(l.a, p, n);
+	let view: str;
+	view.ptr = p;
+	view.len = n: i32;
+	out.text = strings.dup(view);
 };
 
 fn lexstr(l: *lex, start: *pos, out: *tok) void = {
@@ -4288,7 +4301,10 @@ fn lexstr(l: *lex, start: *pos, out: *tok) void = {
 			out.file = start.file;
 	out.line = start.line;
 	out.col  = start.col;
-			out.text = astrndup(l.a, "".ptr, 0u64);
+			let view: str;
+			view.ptr = "".ptr;
+			view.len = 0;
+			out.text = strings.dup(view);
 			return;
 		};
 		if (c == 34) { lget(l); break; };
@@ -4333,7 +4349,10 @@ fn lexrune(l: *lex, start: *pos, out: *tok) void = {
 		out.file = start.file;
 	out.line = start.line;
 	out.col  = start.col;
-		out.text = astrndup(l.a, "".ptr, 0u64);
+		let view: str;
+		view.ptr = "".ptr;
+		view.len = 0;
+		out.text = strings.dup(view);
 		return;
 	};
 	let ch: i32 = 0;
@@ -4349,7 +4368,10 @@ fn lexrune(l: *lex, start: *pos, out: *tok) void = {
 		out.file = start.file;
 	out.line = start.line;
 	out.col  = start.col;
-		out.text = astrndup(l.a, "".ptr, 0u64);
+		let view: str;
+		view.ptr = "".ptr;
+		view.len = 0;
+		out.text = strings.dup(view);
 		return;
 	};
 	lget(l);
@@ -4503,7 +4525,10 @@ export fn lexnext(l: *lex, out: *tok) void = {
 	setposfrom(out, &start);
 	let one: [1]u8;
 	one[0] = c: u8;
-	out.text = astrndup(l.a, one.ptr, 1u64);
+	let view: str;
+	view.ptr = one.ptr;
+	view.len = 1;
+	out.text = strings.dup(view);
 };
 
 // lib/ww/ast.ww — port of cmd/wcc/ast.c (Node defs + printer).