Web UI: runtime console + KV session panel, with runtime/storage libs and tests (#32)

* Add web runtime console and KV sessions

* test(web): cover runtime and KV session behavior

* Fix runtime helper formatting

web/src/lib/runtime.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, it } from "vitest"
+
+import type { HealthResponse } from "./api"
+import { activeRequests, supportsCacheSlots } from "./runtime"
+
+const healthWithActive = (active: boolean | number): HealthResponse => ({
+  status: "ok",
+  scheduler: {
+    active,
+    queued: 0,
+    max_queue: 0,
+    queue_timeout_seconds: 0,
+    admitted: 0,
+    completed: 0,
+    rejected: 0,
+    timed_out: 0,
+    cancelled: 0,
+  },
+})
+
+describe("runtime capability normalization", () => {
+  it.each([
+    [true, 1],
+    [false, 0],
+    [3, 3],
+    [0, 0],
+  ] as const)("normalizes scheduler.active %s to %d", (active, expected) => {
+    expect(activeRequests(healthWithActive(active))).toBe(expected)
+  })
+
+  it("treats missing scheduler metrics as idle", () => {
+    expect(activeRequests({ status: "ok" })).toBe(0)
+    expect(activeRequests(null)).toBe(0)
+  })
+
+  it("only enables cache slots when the health response advertises them", () => {
+    expect(supportsCacheSlots({ status: "ok", kv_slots: 4 })).toBe(true)
+    expect(supportsCacheSlots({ status: "ok" })).toBe(false)
+    expect(supportsCacheSlots(null)).toBe(false)
+  })
+})