Add --test mode to elc with Assert stmt and full native test suite passing

Implement compile_test() entry point that emits a C test harness instead
of a normal program. Test blocks (previously skipped) now compile to
static functions with per-assertion pass/fail tracking. Assert statement
added to parser and codegen. Runtime extended with now_ns, fs_list_json,
json_build_object, json_build_array, json_escape_string, state_has,
state_get_or. Fix float negation codegen, float equality comparisons,
time_to_parts return type (JSON string), time_format empty-fmt, json_set
raw-value semantics, state_keys JSON array return. All 310 native tests
pass across 9 suites (core, text, string, math, env, state, json, time, fs).

lang/el-compiler/src/compiler.el

@@ -41,6 +41,20 @@ fn compile(source: String) -> String {
     ""
 }
 
+// compile_test — like compile() but sets __test_mode so codegen_streaming
+// compiles test { } blocks instead of skipping them, and emits the test
+// harness main() instead of the normal int main().
+fn compile_test(source: String) -> String {
+    state_set("__test_mode", "1")
+    let top_mark: Any = el_arena_push()
+    let tokens: [Any] = lex(source)
+    let sigs: [Map<String, Any>] = scan_fn_sigs(tokens)
+    codegen_streaming(tokens, sigs, source)
+    el_arena_pop(top_mark)
+    state_set("__test_mode", "")
+    ""
+}
+
 // compile_js — full pipeline (JS target, module mode): source string -> JS source string
 fn compile_js(source: String) -> String {
     let tokens: [Any] = lex(source)
@@ -159,6 +173,18 @@ fn detect_obfuscate(argv: [String]) -> Bool {
     return false
 }
 
+// Detect --test flag in argv.
+fn detect_test(argv: [String]) -> Bool {
+    let n: Int = native_list_len(argv)
+    let i = 0
+    while i < n {
+        let a: String = native_list_get(argv, i)
+        if str_eq(a, "--test") { return true }
+        let i = i + 1
+    }
+    return false
+}
+
 // Build a unique temp file path: /tmp/elc-<pid>-<timestamp>.<suffix>
 fn make_temp_path(suffix: String) -> String {
     let pid: Int = getpid_now()
@@ -488,6 +514,7 @@ fn main() -> Void {
     let do_bundle: Bool = detect_bundle(argv)
     let do_minify: Bool = detect_minify(argv)
     let do_obfuscate: Bool = detect_obfuscate(argv)
+    let do_test: Bool = detect_test(argv)
     // --obfuscate implies --minify: obfuscating unminified code is pointless.
     if do_obfuscate {
         let do_minify = true
@@ -495,7 +522,7 @@ fn main() -> Void {
     let positional: [String] = strip_flags(argv)
     let argc: Int = native_list_len(positional)
     if argc < 1 {
-        println("el-compiler: usage: elc [--target=c|js] [--bundle] [--minify] [--obfuscate] [--emit-header] <source.el> [<output>]")
+        println("el-compiler: usage: elc [--target=c|js] [--bundle] [--minify] [--obfuscate] [--emit-header] [--test] <source.el> [<output>]")
         exit(1)
     }
 
@@ -532,6 +559,12 @@ fn main() -> Void {
         exit(0)
     }
 
+    // --test mode: compile with test harness (C target only).
+    if do_test {
+        compile_test(source)
+        exit(0)
+    }
+
     // Standard path (no post-processing).
     let out: String = ""
     if do_bundle {