Show in-flight request count + activity spark on In-Flight Monitor key

The key now renders the live request count (large) when a model is active,
plus a 1Hz count-trend sparkline of the last 60s in a bottom strip. IDLE/
LOADING/OFF/OFFLINE states unchanged. History lives in per-key state with
a sampler cleared on disappear.

tests/render.test.ts

@@ -14,10 +14,31 @@ test("renderInflight: ready + count renders IDLE in green", () => {
   assert.doesNotMatch(svg, /ACTIVE/);
 });
 
-test("renderInflight: ready + count>0 renders ACTIVE in red", () => {
+test("renderInflight: ready + count>0 renders the count number on red", () => {
   const svg = renderInflight({ modelName: "Qwen3.8-27B-NVFP4", state: "ready", count: 2, offline: false, pulse: false });
-  assert.match(svg, /ACTIVE/);
+  assert.match(svg, /2/);
   assert.match(svg, /#8b2626/);
+  assert.doesNotMatch(svg, /ACTIVE/);
+  assert.doesNotMatch(svg, /IDLE/);
+});
+
+test("renderInflight: idle state does not show a count number", () => {
+  const svg = renderInflight({ modelName: "A", state: "ready", count: 0, offline: false, pulse: false });
+  assert.match(svg, /IDLE/);
+  assert.doesNotMatch(svg, /font-size="24"/);
+});
+
+test("renderInflight: draws a count-trend spark when history has 2+ samples", () => {
+  const svg = renderInflight({ modelName: "A", state: "ready", count: 1, offline: false, pulse: false, history: [0, 1, 2, 1] });
+  assert.match(svg, /<polyline/);
+  assert.match(svg, /<path/);
+});
+
+test("renderInflight: no spark with fewer than 2 history samples", () => {
+  const svg = renderInflight({ modelName: "A", state: "ready", count: 1, offline: false, pulse: false, history: [1] });
+  assert.doesNotMatch(svg, /<polyline/);
+  const none = renderInflight({ modelName: "A", state: "ready", count: 1, offline: false, pulse: false });
+  assert.doesNotMatch(none, /<polyline/);
 });
 
 test("renderInflight: pulse toggles opacity while active", () => {