Quiet the debug-noise that was lagging the browser

You're right — the telemetry path itself was contributing to perceived
browser lag, not just the GPU work. Two specific sources removed:

render/mod.rs::rebuild_chunk:
  - Per-chunk log::info!("rebuild_chunk {coord}: {ms}ms ...") fired
    ~289 times during world init, plus on every edit. Chrome's console
    buffer accumulates these and DevTools recalcs on each new line.
    Removed entirely. The bench toggles + FPS HUD already give us the
    measurement signal; per-chunk timing was noise once verified.

web/main.js setupFpsHud:
  - Was a 5 Hz setInterval that did `el.textContent = ...` and two
    `classList.toggle` calls each tick (15 DOM writes/sec). Now:
      * Polls at 1 Hz (the EMA already smooths)
      * Only writes textContent when the displayed string actually
        changes (skip is the common case once stabilized)
      * Only writes class when the tier (green/warn/bad) crosses
        a threshold
    Same readout, ~15× fewer DOM writes.

web/main.js setupStatusLoop (HP bar):
  - Same dedupe pattern. 10 Hz polling, but DOM writes only when
    hp or alive changes from the last sample. Was firing 3 style
    writes per tick unconditionally; now zero in steady state.

No functionality changes — every telemetry getter, every bench
toggle, every test-harness export still works (just verified via
the 18-check functional contract suite).

Wasm release built; tests 63/63 pass.

src/render/mod.rs

@@ -507,20 +507,12 @@ impl Renderer {
         // immutable &World into build_chunk_mesh while still owning
         // &mut self below.
         let chunk_clone = chunk.clone();
-        let t0 = browser_now();
+        // Mesh build no longer logs per chunk — the per-frame spam
+        // (~289 entries during init) was filling the browser console
+        // and contributing to perceived browser lag, especially with
+        // DevTools open. Use the FPS HUD / bench toggles for runtime
+        // perf measurement instead.
         let mesh = build_chunk_mesh(world, &chunk_clone);
-        let mesh_ms = browser_now() - t0;
-        // Lowered threshold so the heightmap-fast path also surfaces
-        // in telemetry. Tune up later if it gets noisy.
-        if mesh_ms > 0.5 {
-            log::info!(
-                "rebuild_chunk {:?}: {:.1}ms ({} verts, {} idx)",
-                coord,
-                mesh_ms,
-                mesh.vertices.len(),
-                mesh.indices.len()
-            );
-        }
         if mesh.indices.is_empty() {
             self.chunk_buffers.remove(&coord);
             return;

web/main.js

@@ -202,12 +202,24 @@ function setupMenu() {
 function setupStatusLoop() {
   const hpFill = document.getElementById("hp-fill");
   const hpLabel = document.getElementById("hp-label");
+  let lastHp = -1;
+  let lastAlive = null;
   setInterval(() => {
     const hp = wasm.get_hp();
     const alive = wasm.is_alive();
-    hpFill.style.width = (hp / 20 * 100) + "%";
+    // Dedupe: only touch the DOM when something actually changed.
-    hpLabel.textContent = `${hp} / 20`;
+    // Pre-change the loop ran 10× per second and fired three style
-    document.body.classList.toggle("dead", !alive);
+    // writes each time — every frame paying a recalc cost even when
+    // HP held steady. Worth-only-noticeable when the value changes.
+    if (hp !== lastHp) {
+      hpFill.style.width = (hp / 20 * 100) + "%";
+      hpLabel.textContent = `${hp} / 20`;
+      lastHp = hp;
+    }
+    if (alive !== lastAlive) {
+      document.body.classList.toggle("dead", !alive);
+      lastAlive = alive;
+    }
   }, 100);
 }
 
@@ -678,22 +690,31 @@ function cycleHotbar(delta) {
   wasm.select_block(b);
 }
 
-// FPS HUD — reads the EMA-smoothed dt published by App::publish_telemetry
+// FPS HUD — reads the EMA-smoothed dt from the game and writes it
-// each frame. Polled every 200ms (5Hz) which is plenty for a readable
+// once a second. The previous version polled at 5 Hz with DOM writes
-// number without adding measurable overhead. Coloring: green ≤ 18ms,
+// every poll, which on weak hardware contributed to perceived browser
-// amber 18-33ms, red beyond.
+// lag. 1 Hz is more than enough to read the number; the EMA already
+// smooths anything faster anyway. Also skips DOM writes when the
+// reported value hasn't changed enough to display differently.
 function setupFpsHud() {
   const el = document.getElementById("fps");
   if (!el) return;
+  let lastText = "";
+  let lastTier = "";
   setInterval(() => {
     const dt = wasm.get_frame_dt_ms ? wasm.get_frame_dt_ms() : 0;
     if (!dt || dt <= 0) {
-      el.textContent = "— fps";
+      if (lastText !== "— fps") { el.textContent = "— fps"; lastText = "— fps"; }
       return;
     }
     const fps = 1000 / dt;
-    el.textContent = `${fps.toFixed(0)} fps  (${dt.toFixed(1)}ms)`;
+    const next = `${fps.toFixed(0)} fps  (${dt.toFixed(1)}ms)`;
-    el.classList.toggle("warn", dt > 18 && dt <= 33);
+    if (next !== lastText) { el.textContent = next; lastText = next; }
-    el.classList.toggle("bad", dt > 33);
+    const tier = dt > 33 ? "bad" : dt > 18 ? "warn" : "";
-  }, 200);
+    if (tier !== lastTier) {
+      el.classList.toggle("warn", tier === "warn");
+      el.classList.toggle("bad",  tier === "bad");
+      lastTier = tier;
+    }
+  }, 1000);
 }