std: restructure — std/ modules, namespace tail, std/xml.sx

allocators/fs/process/socket/log/trace/test move under modules/std/
(allocators.sx becomes std/mem.sx; the Allocator protocol moves into
the std.sx prelude, impls stay in mem.sx). New std/xml.sx holds
xml_escape as xml.escape. std.sx gains the carried namespace tail —
flat-importing std.sx now also provides mem./xml./log. — with the
remaining modules (fs/process/socket/json/cli/hash/test) deferred from
the tail until the global last-wins maps are fully own-wins (pulling
them into every closure collides bare names corpus-wide; they stay
direct imports: modules/std/fs.sx etc.). log.sx's internal emit
renamed log_emit (it clobbered consumer fns named emit program-wide).
bundle.sx uses xml.escape via the carried alias. Consumer import paths
swept mechanically; .ir snapshots recaptured for the larger std
closure. m3te + game build unchanged.

library/modules/std.sx

@@ -36,7 +36,14 @@ Source_Location :: struct {
 }
 string :: []u8 #builtin;
 
-#import "allocators.sx";
+#import "std/mem.sx";
+
+// --- Allocator protocol (impls live in std/mem.sx) ---
+
+Allocator :: protocol #inline {
+    alloc :: (size: s64) -> *void;
+    dealloc :: (ptr: *void);
+}
 
 // --- Context ---
 
@@ -215,37 +222,6 @@ substr :: (s: string, start: s64, len: s64) -> string {
     buf
 }
 
-// Replace XML special characters with their entity references. Used
-// when emitting Info.plist / AndroidManifest content from sx values
-// that may contain user-supplied text (bundle id, app name, etc).
-xml_escape :: (s: string) -> string {
-    result := "";
-    i := 0;
-    seg_start := 0;
-    while i < s.len {
-        c := s[i];
-        // 38='&', 60='<', 62='>', 34='"', 39='\''
-        ent := "";
-        if c == 38 { ent = "&amp;"; }
-        if c == 60 { ent = "&lt;"; }
-        if c == 62 { ent = "&gt;"; }
-        if c == 34 { ent = "&quot;"; }
-        if c == 39 { ent = "&apos;"; }
-        if ent.len > 0 {
-            if i > seg_start {
-                result = concat(result, substr(s, seg_start, i - seg_start));
-            }
-            result = concat(result, ent);
-            seg_start = i + 1;
-        }
-        i += 1;
-    }
-    if seg_start < s.len {
-        result = concat(result, substr(s, seg_start, s.len - seg_start));
-    }
-    result
-}
-
 // Join path components with the POSIX separator ('/'). Skips empty
 // components and collapses duplicate separators at component
 // boundaries. Used for bundle paths where Apple .app and Android APK
@@ -513,4 +489,13 @@ List :: struct ($T: Type) {
         list.len = 0;
         list.cap = 0;
     }
-}
+}
+// --- The stdlib namespace tail: flat-importing std.sx carries these ---
+
+mem :: #import "std/mem.sx";
+xml :: #import "std/xml.sx";
+log :: #import "std/log.sx";
+// fs/process/socket/json/cli/hash/test join the tail once the global
+// last-wins maps are fully own-wins (their decls collide across programs
+// when pulled into every closure) — import them directly meanwhile:
+//   #import "modules/std/fs.sx";  etc.