test framework phase 1: compile-time registry + El-side runner

Replace the hardcoded test harness main() with a generated static registry
and index-based accessors, and move all reporting into runtime/eltest.el.

The old harness inlined direct calls into main() and counted assertions in
two globals. That shape cannot report which test failed, how long any test
took, or whether a test ran at all -- a misspelled registration reported
success for a test that never executed.

- assertions record into per-test state instead of global counters
- registry table emitted at compile time; discovery strictly precedes
  execution, which is what later enables --list, filtering and sharding
- per-test wall timing on CLOCK_MONOTONIC, taken in C around the call
- runner in El: structured NDJSON events as source of truth, human output
  rendered from the same fields

lang/el-compiler/src/codegen.el

@@ -1705,9 +1705,13 @@ fn cg_stmt(stmt: Map<String, Any>, indent: String, declared: [String]) -> [Strin
         } else {
             let c_msg = "EL_STR_PTR(" + cg_expr(msg_node) + ")"
         }
+        // Assertions record into PER-TEST state, not global counters. The test
+        // is the unit of result; a global pass/fail tally cannot say which test
+        // failed or whether a test ran at all. Reporting is the runner's job —
+        // nothing is printed here.
         emit_line(indent + "if (!(" + c_cond + ")) {")
-        emit_line(indent + "  __el_test_fail(__el_cur_test, " + c_msg + "); __el_fail++;")
-        emit_line(indent + "} else { __el_pass++; }")
+        emit_line(indent + "  __el_test_fail(" + c_msg + ");")
+        emit_line(indent + "} else { __el_cur_asserts++; }")
         return declared
     }
 
@@ -4110,11 +4114,22 @@ fn codegen_streaming(tokens: [Any], sigs: [Map<String, Any>], source: String) ->
     // Emit test harness preamble (counters, fail printer) when in test mode.
     if test_is_mode {
         emit_line("#include <stdio.h>")
+        emit_line("#include <string.h>")
+        emit_line("#include <time.h>")
         emit_blank()
-        emit_line("static int __el_pass = 0, __el_fail = 0;")
+        // Per-test result state. Reset by __el_reg_invoke before each test, so
+        // every test gets its own record rather than contributing to a global
+        // tally. The first failure message is retained; later ones only bump
+        // the count, which keeps the common case allocation-free.
+        emit_line("static int __el_cur_fails = 0;")
+        emit_line("static int __el_cur_asserts = 0;")
+        emit_line("static char __el_cur_msg[512] = \"\";")
         emit_line("static const char *__el_cur_test = \"(none)\";")
-        emit_line("static void __el_test_fail(const char *test, const char *msg) {")
-        emit_line("  fprintf(stderr, \"FAIL  %-40s %s\\n\", test, msg);")
+        emit_line("static void __el_test_fail(const char *msg) {")
+        emit_line("  if (__el_cur_fails == 0 && msg) {")
+        emit_line("    snprintf(__el_cur_msg, sizeof __el_cur_msg, \"%s\", msg);")
+        emit_line("  }")
+        emit_line("  __el_cur_fails++; __el_cur_asserts++;")
         emit_line("}")
         emit_blank()
     }
@@ -4312,17 +4327,72 @@ fn codegen_streaming(tokens: [Any], sigs: [Map<String, Any>], source: String) ->
         el_release(sigs)
 
         let test_arena_mark: Any = el_arena_push()
+        let tn: Int = native_list_len(test_c_names)
+
+        // ── Generated test registry ──────────────────────────────────────────
+        // Discovery happens HERE, at compile time. The runner never searches
+        // for tests; it walks this table. That ordering — discovery strictly
+        // before execution — is what makes --list, filtering, sharding and
+        // per-test reporting possible later, and it is why the old harness
+        // (which inlined direct calls into main) could not have any of them.
+        emit_line("typedef void (*__el_test_fp)(void);")
+        emit_line("typedef struct { const char *name; __el_test_fp fn; } __el_test_entry;")
+        emit_line("static const __el_test_entry __el_registry[] = {")
+        let ri: Int = 0
+        while ri < tn {
+            let r_name: String = native_list_get(test_names, ri)
+            let r_cfn: String = native_list_get(test_c_names, ri)
+            emit_line("  { \"" + c_escape(r_name) + "\", " + r_cfn + " },")
+            let ri = ri + 1
+        }
+        // Trailing sentinel keeps the array non-empty when a file declares no
+        // tests (a zero-length array is not valid C).
+        emit_line("  { 0, 0 }")
+        emit_line("};")
+        emit_line("static const int __el_registry_n = " + int_to_str(tn) + ";")
+        emit_blank()
+        emit_line("static long long __el_last_ns = 0;")
+        emit_line("static int __el_opt_json_v = 0;")
+        emit_blank()
+
+        // ── Index-based accessors ────────────────────────────────────────────
+        // El has no function pointers, so the runner works purely in indices.
+        // This is the whole seam between generated C and the El-side runner.
+        emit_line("el_val_t __el_reg_count(void) { return (el_val_t)(int64_t)__el_registry_n; }")
+        emit_line("el_val_t __el_reg_name(el_val_t i) {")
+        emit_line("  int64_t k = (int64_t)i;")
+        emit_line("  if (k < 0 || k >= __el_registry_n) return EL_STR(\"\");")
+        emit_line("  return EL_STR(__el_registry[k].name);")
+        emit_line("}")
+        // Timing is taken immediately around the call, in C, on the MONOTONIC
+        // clock — never the wall clock, which can step backwards under NTP.
+        emit_line("el_val_t __el_reg_invoke(el_val_t i) {")
+        emit_line("  int64_t k = (int64_t)i;")
+        emit_line("  if (k < 0 || k >= __el_registry_n) return 0;")
+        emit_line("  __el_cur_fails = 0; __el_cur_asserts = 0; __el_cur_msg[0] = '\\0';")
+        emit_line("  __el_cur_test = __el_registry[k].name;")
+        emit_line("  struct timespec _t0, _t1;")
+        emit_line("  clock_gettime(CLOCK_MONOTONIC, &_t0);")
+        emit_line("  __el_registry[k].fn();")
+        emit_line("  clock_gettime(CLOCK_MONOTONIC, &_t1);")
+        emit_line("  __el_last_ns = (long long)(_t1.tv_sec - _t0.tv_sec) * 1000000000LL")
+        emit_line("              + (long long)(_t1.tv_nsec - _t0.tv_nsec);")
+        emit_line("  return (el_val_t)(int64_t)__el_cur_fails;")
+        emit_line("}")
+        emit_line("el_val_t __el_reg_last_ns(void) { return (el_val_t)(int64_t)__el_last_ns; }")
+        emit_line("el_val_t __el_reg_msg(void) { return EL_STR(__el_cur_msg); }")
+        emit_line("el_val_t __el_reg_asserts(void) { return (el_val_t)(int64_t)__el_cur_asserts; }")
+        emit_line("el_val_t __el_opt_json(void) { return (el_val_t)(int64_t)__el_opt_json_v; }")
+        emit_blank()
+
+        // main() delegates to the El-side runner. Everything above this line is
+        // generated glue; all reporting logic lives in runtime/eltest.el.
         emit_line("int main(int _argc, char **_argv) {")
         emit_line("  el_runtime_init_args(_argc, _argv);")
-        let ti: Int = 0
-        let tn: Int = native_list_len(test_c_names)
-        while ti < tn {
-            let tc_name: String = native_list_get(test_c_names, ti)
-            emit_line("  " + tc_name + "();")
-            let ti = ti + 1
-        }
-        emit_line("  printf(\"%d passed, %d failed\\n\", __el_pass, __el_fail);")
-        emit_line("  return __el_fail;")
+        emit_line("  for (int _i = 1; _i < _argc; _i++) {")
+        emit_line("    if (strcmp(_argv[_i], \"--json\") == 0) __el_opt_json_v = 1;")
+        emit_line("  }")
+        emit_line("  return (int)(int64_t)el_test_main();")
         emit_line("}")
         el_arena_pop(test_arena_mark)
         el_release(test_names)