fix(lsp): remove unreliable Windows binary availability check

The isBinaryAvailableOnWindows() function used spawnSync("where")

which fails even when the binary IS on PATH, causing false negatives.

Removed the redundant pre-check and let nodeSpawn handle binary

resolution naturally with proper OS-level error messages.

Fixes #1805

src/tools/lsp/lsp-process.test.ts

@@ -0,0 +1,37 @@
+import { mkdtempSync, rmSync } from "node:fs"
+import { tmpdir } from "node:os"
+import { join } from "node:path"
+
+import { describe, expect, it, spyOn } from "bun:test"
+
+describe("spawnProcess", () => {
+  it("proceeds to node spawn on Windows when command is available", async () => {
+    // #given
+    const originalPlatform = process.platform
+    const rootDir = mkdtempSync(join(tmpdir(), "lsp-process-test-"))
+    const childProcess = await import("node:child_process")
+    const nodeSpawnSpy = spyOn(childProcess, "spawn")
+
+    try {
+      Object.defineProperty(process, "platform", { value: "win32" })
+      const { spawnProcess } = await import("./lsp-process")
+
+      // #when
+      let result: ReturnType<typeof spawnProcess> | null = null
+      expect(() => {
+        result = spawnProcess(["node", "--version"], {
+          cwd: rootDir,
+          env: process.env,
+        })
+      }).not.toThrow(/Binary 'node' not found/)
+
+      // #then
+      expect(nodeSpawnSpy).toHaveBeenCalled()
+      expect(result).not.toBeNull()
+    } finally {
+      Object.defineProperty(process, "platform", { value: originalPlatform })
+      nodeSpawnSpy.mockRestore()
+      rmSync(rootDir, { recursive: true, force: true })
+    }
+  })
+})