fix(dashboard): write ChatView visualViewport vars imperatively

The mobile composer/footer slid over the message list when the user
swiped with the keyboard up. Cause: --vv-height / --vv-offset-top were
routed through React state via useMobileKeyboard, so on iOS — which
fires visualViewport scroll/resize on the same frame as its keyboard
animation — the .chat-thread translation lagged by one paint, visible
as the composer momentarily floating over messages.

Now those two vars are written imperatively in a useLayoutEffect
directly to the .chat-thread DOM node on every visualViewport event,
mirroring the working pattern at QuickChatFAB.tsx:1032-1052 (which
already works correctly on mobile). Only --keyboard-overlap (a
structural open/close signal, not per-frame) still flows through
React state.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugins/fusion-plugin-hermes-runtime/dist/__tests__/probe.test.js

@@ -0,0 +1,107 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { EventEmitter } from "node:events";
+// ── Mock node:child_process ────────────────────────────────────────────────
+const { mockSpawn } = vi.hoisted(() => ({ mockSpawn: vi.fn() }));
+vi.mock("node:child_process", () => ({ spawn: mockSpawn }));
+import { probeHermesBinary } from "../probe.js";
+// ── Helpers ────────────────────────────────────────────────────────────────
+/** Yields to the microtask and I/O queue so awaited code can continue. */
+function flushAsync() {
+    return new Promise((resolve) => setImmediate(resolve));
+}
+function makeFakeChild() {
+    const main = new EventEmitter();
+    const stdoutEmitter = new EventEmitter();
+    const stderrEmitter = new EventEmitter();
+    main.stdout = stdoutEmitter;
+    main.stderr = stderrEmitter;
+    main.kill = vi.fn();
+    return {
+        child: main,
+        emitStdout: (data) => stdoutEmitter.emit("data", Buffer.from(data)),
+        emitStderr: (data) => stderrEmitter.emit("data", Buffer.from(data)),
+        emitError: (err) => main.emit("error", err),
+        emitClose: (code) => main.emit("close", code),
+    };
+}
+// ── Tests ──────────────────────────────────────────────────────────────────
+describe("probeHermesBinary", () => {
+    beforeEach(() => {
+        vi.clearAllMocks();
+    });
+    it("returns available: false with not-found reason on ENOENT", async () => {
+        // probeHermesBinary first awaits tryResolveBinaryPath (which/where spawn),
+        // then spawns the --version process. We must drive them sequentially.
+        const whichChild = makeFakeChild();
+        const versionChild = makeFakeChild();
+        mockSpawn
+            .mockReturnValueOnce(whichChild.child) // which hermes
+            .mockReturnValueOnce(versionChild.child); // hermes --version
+        const promise = probeHermesBinary({ timeoutMs: 500 });
+        // Settle the `which` call — which causes tryResolveBinaryPath to resolve.
+        whichChild.emitClose(1);
+        // Yield so the awaited tryResolveBinaryPath continuation runs and spawns
+        // the version child before we emit its error.
+        await flushAsync();
+        const enoent = Object.assign(new Error("ENOENT"), { code: "ENOENT" });
+        versionChild.emitError(enoent);
+        const result = await promise;
+        expect(result.available).toBe(false);
+        expect(result.reason).toMatch(/not found on PATH/);
+        expect(result.probeDurationMs).toBeGreaterThanOrEqual(0);
+    });
+    it("returns available: true with parsed version on success", async () => {
+        const whichChild = makeFakeChild();
+        const versionChild = makeFakeChild();
+        mockSpawn
+            .mockReturnValueOnce(whichChild.child)
+            .mockReturnValueOnce(versionChild.child);
+        const promise = probeHermesBinary({ binaryPath: "hermes", timeoutMs: 500 });
+        whichChild.emitStdout("/usr/local/bin/hermes\n");
+        whichChild.emitClose(0);
+        await flushAsync();
+        versionChild.emitStdout("Hermes Agent v1.2.3\n");
+        versionChild.emitClose(0);
+        const result = await promise;
+        expect(result.available).toBe(true);
+        expect(result.version).toBe("Hermes Agent v1.2.3");
+        expect(result.binaryPath).toBe("/usr/local/bin/hermes");
+        expect(result.reason).toBeUndefined();
+        expect(result.probeDurationMs).toBeGreaterThanOrEqual(0);
+    });
+    it("returns available: false when version exits non-zero", async () => {
+        const whichChild = makeFakeChild();
+        const versionChild = makeFakeChild();
+        mockSpawn
+            .mockReturnValueOnce(whichChild.child)
+            .mockReturnValueOnce(versionChild.child);
+        const promise = probeHermesBinary({ timeoutMs: 500 });
+        whichChild.emitClose(1);
+        await flushAsync();
+        versionChild.emitStderr("error: something went wrong");
+        versionChild.emitClose(2);
+        const result = await promise;
+        expect(result.available).toBe(false);
+        expect(result.reason).toContain("error: something went wrong");
+    });
+    it("uses custom binaryPath when provided", async () => {
+        const whichChild = makeFakeChild();
+        const versionChild = makeFakeChild();
+        mockSpawn
+            .mockReturnValueOnce(whichChild.child)
+            .mockReturnValueOnce(versionChild.child);
+        const promise = probeHermesBinary({ binaryPath: "/opt/bin/hermes", timeoutMs: 500 });
+        whichChild.emitClose(1);
+        await flushAsync();
+        versionChild.emitStdout("Hermes Agent v2.0.0\n");
+        versionChild.emitClose(0);
+        const result = await promise;
+        expect(result.available).toBe(true);
+        expect(result.version).toBe("Hermes Agent v2.0.0");
+        // Verify the version spawn used our custom path.
+        const versionSpawnArgs = mockSpawn.mock.calls[1];
+        expect(versionSpawnArgs[0]).toBe("/opt/bin/hermes");
+        expect(versionSpawnArgs[1]).toEqual(["--version"]);
+    });
+});
+//# sourceMappingURL=probe.test.js.map