feat: std.http handler carries an opaque ctx word (PLAN-HTTPZ A1 prep)

Server.init(cfg, handler, ctx); the handler signature gains a usize
third argument delivered verbatim per dispatch — typically a pointer
to the app's own state, since the server owns the call site. A bare
(req, resp) handler had no way to reach app state without globals.
examples/1633 pins the round trip.

examples/1633-http-server.sx

@@ -7,9 +7,11 @@
 
 PORT :: 18933;
 
-handler :: (req: *http.Request, resp: *http.Response) {
+handler :: (req: *http.Request, resp: *http.Response, ctx: usize) {
     if req.path == "/hello" {
         resp.body = concat("hello ", req.method);
+        // the ctx word arrives verbatim (init passed 77)
+        if ctx != 77 { resp.status = 500; resp.body = "ctx lost"; }
         return;
     }
     if req.path == "/echo" {
@@ -105,7 +107,7 @@ main :: () -> i32 {
         request_count = 3,
         max_conn = 8,
     };
-    srv, se := http.Server.init(cfg, handler);
+    srv, se := http.Server.init(cfg, handler, 77);
     if se { print("server init failed\n"); return 1; }
 
     buf : [4096]u8 = ---;

examples/expected/1202-ffi-cc-c-large-aggregate.ir

@@ -897,7 +897,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1309-ffi-objc-class-method-lowering.ir

@@ -1389,7 +1389,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1314-ffi-objc-class-dealloc-roundtrip.ir

@@ -1405,7 +1405,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1329-ffi-objc-call-03-selector-sharing.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1347-ffi-objc-dsl-07-mangling-table.ir

@@ -1407,7 +1407,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1402-ffi-jni-call-03-methodid-sharing.ir

@@ -1383,7 +1383,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1403-ffi-jni-call-04-jint-return.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1404-ffi-jni-call-05-jlong-return.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1405-ffi-jni-call-06-jdouble-return.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1406-ffi-jni-call-07-jboolean-return.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1407-ffi-jni-call-08-jobject-return.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1408-ffi-jni-call-09-static.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1418-ffi-jni-class-08-call.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1421-ffi-jni-env-02-lexical-direct.ir

@@ -1381,7 +1381,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

examples/expected/1425-ffi-jni-main-03-ctor.ir

@@ -904,7 +904,7 @@ declare i1 @ascii_ieq(ptr, ptr, ptr) #0
 declare ptr @reason_for(ptr, i64) #0
 
 ; Function Attrs: nounwind
-declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr }, i32 }), ptr, ptr, ptr) #0
+declare void @Server.init(ptr sret({ { { i64, i32, i64, i64, i64, i64, i64 }, { i32 }, i32, ptr, { ptr, ptr, ptr }, ptr, i64 }, i32 }), ptr, ptr, ptr, i64) #0
 
 ; Function Attrs: nounwind
 declare void @Server.close(ptr, ptr) #0

library/modules/std/http.sx

@@ -145,9 +145,13 @@ Server :: struct {
     lfd: i32 = -1;
     conns: [*]Conn = null;
     own_alloc: Allocator;
-    handler: (*Request, *Response) -> void;
+    // The handler's third argument is `ctx`, an opaque word the app
+    // gave init — typically a pointer to its own state (store handle,
+    // config), since the server owns the call site.
+    handler: (*Request, *Response, usize) -> void;
+    ctx: usize = 0;
 
-    init :: (cfg: Config, handler: (*Request, *Response) -> void) -> (Server, !HttpErr) {
+    init :: (cfg: Config, handler: (*Request, *Response, usize) -> void, ctx: usize) -> (Server, !HttpErr) {
         lfd := socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0);
         if lfd < 0 { raise error.Bind; }
         one : i32 = 1;
@@ -175,7 +179,7 @@ Server :: struct {
         }
         return Server.{
             cfg = cfg, loop = lp, lfd = lfd, conns = slots,
-            own_alloc = oa, handler = handler,
+            own_alloc = oa, handler = handler, ctx = ctx,
         };
     }
 
@@ -401,7 +405,7 @@ Server :: struct {
         // be parsed as a dot-call on a function named `handler`)
         h := self.handler;
         resp : Response = .{};
-        h(@req, @resp);
+        h(@req, @resp, self.ctx);
 
         c.served += 1;
         keep := req.keep_alive and c.served < self.cfg.request_count;