vm/router: minimal special-method extension (equals/1); toString mapping kept

mir: add TypeCertainty to Callee::Method (diagnostic only); plumb through builder/JSON/printer; backends ignore behaviorally

using: confirm unified prelude resolver entry for all runner modes

docs: update Callee architecture with certainty; update call-instructions; CURRENT_TASK note

tests: quick 40/40 PASS; integration (LLVM) 17/17 PASS

src/debug/hub.rs

@@ -0,0 +1,36 @@
+use std::io::Write;
+
+/// Minimal debug hub: JSONL event emitter (dev-only; default OFF).
+///
+/// Env knobs:
+/// - NYASH_DEBUG_ENABLE=1           master gate
+/// - NYASH_DEBUG_KINDS=resolve,ssa  allowed cats (comma-separated)
+/// - NYASH_DEBUG_SINK=path          file to append JSONL events
+pub fn emit(cat: &str, kind: &str, fn_name: Option<&str>, region_id: Option<&str>, meta: serde_json::Value) {
+    if std::env::var("NYASH_DEBUG_ENABLE").ok().as_deref() != Some("1") {
+        return;
+    }
+    if let Ok(kinds) = std::env::var("NYASH_DEBUG_KINDS") {
+        if !kinds.split(',').any(|k| k.trim().eq_ignore_ascii_case(cat)) {
+            return;
+        }
+    }
+    let sink = match std::env::var("NYASH_DEBUG_SINK") {
+        Ok(s) if !s.is_empty() => s,
+        _ => return,
+    };
+    let ts = chrono::Utc::now().to_rfc3339_opts(chrono::SecondsFormat::Millis, true);
+    let obj = serde_json::json!({
+        "ts": ts,
+        "phase": "builder",
+        "fn": fn_name.unwrap_or("<unknown>"),
+        "region_id": region_id.unwrap_or(""),
+        "cat": cat,
+        "kind": kind,
+        "meta": meta,
+    });
+    if let Ok(mut f) = std::fs::OpenOptions::new().create(true).append(true).open(&sink) {
+        let _ = writeln!(f, "{}", obj.to_string());
+    }
+}
+