fix(installer): improve Windows compatibility for shell detection and paths

Closes #461

src/shared/data-path.test.ts

@@ -0,0 +1,57 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test"
+import { homedir } from "node:os"
+import { join } from "node:path"
+import { getCacheDir, getDataDir } from "./data-path"
+
+describe("data-path", () => {
+  let originalPlatform: NodeJS.Platform
+  let originalEnv: Record<string, string | undefined>
+
+  beforeEach(() => {
+    originalPlatform = process.platform
+    originalEnv = {
+      LOCALAPPDATA: process.env.LOCALAPPDATA,
+      APPDATA: process.env.APPDATA,
+      XDG_DATA_HOME: process.env.XDG_DATA_HOME,
+      XDG_CACHE_HOME: process.env.XDG_CACHE_HOME,
+    }
+  })
+
+  afterEach(() => {
+    Object.defineProperty(process, "platform", { value: originalPlatform })
+    for (const [key, value] of Object.entries(originalEnv)) {
+      if (value !== undefined) {
+        process.env[key] = value
+      } else {
+        delete process.env[key]
+      }
+    }
+  })
+
+  test("#given Windows with LOCALAPPDATA #when getDataDir is called #then returns LOCALAPPDATA", () => {
+    Object.defineProperty(process, "platform", { value: "win32" })
+    process.env.LOCALAPPDATA = "C:\\Users\\TestUser\\AppData\\Local"
+
+    const result = getDataDir()
+
+    expect(result).toBe("C:\\Users\\TestUser\\AppData\\Local")
+  })
+
+  test("#given Windows without LOCALAPPDATA #when getDataDir is called #then falls back to AppData Local", () => {
+    Object.defineProperty(process, "platform", { value: "win32" })
+    delete process.env.LOCALAPPDATA
+
+    const result = getDataDir()
+
+    expect(result).toBe(join(homedir(), "AppData", "Local"))
+  })
+
+  test("#given Windows with LOCALAPPDATA #when getCacheDir is called #then returns Local cache path", () => {
+    Object.defineProperty(process, "platform", { value: "win32" })
+    process.env.LOCALAPPDATA = "C:\\Users\\TestUser\\AppData\\Local"
+
+    const result = getCacheDir()
+
+    expect(result).toBe(join("C:\\Users\\TestUser\\AppData\\Local", "cache"))
+  })
+})