fix(tests): resolve cross-platform npm and path issues

This commit resolves Windows test failures by addressing two critical issues:

1. npm ENOENT error in integration tests:
   - Added missing PATH environment variable to npm install spawn call
   - Fixes "spawn npm ENOENT" errors on Windows (3 test failures)
   - Tests now properly inherit platform-specific PATH separator

2. Arborist path normalization:
   - Wrapped path.join() results with normalizePath() in all arborist functions
   - Ensures consistent forward-slash paths across platforms
   - Fixes 7 test failures where Windows backslashes caused mismatches

Author: jdalton

packages/cli/src/commands/npm/socket-npm-integration.test.mts

@@ -51,6 +51,10 @@ if (!npmDirs.length) {
           // Ensure npm is installed in the fixture.
           await spawn('npm', ['install', ...(useDebug ? [] : [FLAG_SILENT])], {
             cwd: npmPath,
+            env: {
+              ...process.env,
+              PATH: `${npmBinPath}${pathSep}${ENV.PATH}`,
+            },
             stdio: useDebug ? 'inherit' : 'ignore',
           })
 

packages/cli/src/shadow/npm/paths.mts

@@ -26,9 +26,8 @@ export function getArboristPackagePath() {
 let _arboristClassPath: string | undefined
 export function getArboristClassPath() {
   if (_arboristClassPath === undefined) {
-    _arboristClassPath = path.join(
-      getArboristPackagePath(),
-      'lib/arborist/index.js',
+    _arboristClassPath = normalizePath(
+      path.join(getArboristPackagePath(), 'lib/arborist/index.js'),
     )
   }
   return _arboristClassPath
@@ -37,25 +36,28 @@ export function getArboristClassPath() {
 let _arboristEdgeClassPath: string | undefined
 export function getArboristEdgeClassPath() {
   if (_arboristEdgeClassPath === undefined) {
-    _arboristEdgeClassPath = path.join(getArboristPackagePath(), 'lib/edge.js')
+    _arboristEdgeClassPath = normalizePath(
+      path.join(getArboristPackagePath(), 'lib/edge.js'),
+    )
   }
   return _arboristEdgeClassPath
 }
 
 let _arboristNodeClassPath: string | undefined
 export function getArboristNodeClassPath() {
   if (_arboristNodeClassPath === undefined) {
-    _arboristNodeClassPath = path.join(getArboristPackagePath(), 'lib/node.js')
+    _arboristNodeClassPath = normalizePath(
+      path.join(getArboristPackagePath(), 'lib/node.js'),
+    )
   }
   return _arboristNodeClassPath
 }
 
 let _arboristOverrideSetClassPath: string | undefined
 export function getArboristOverrideSetClassPath() {
   if (_arboristOverrideSetClassPath === undefined) {
-    _arboristOverrideSetClassPath = path.join(
-      getArboristPackagePath(),
-      'lib/override-set.js',
+    _arboristOverrideSetClassPath = normalizePath(
+      path.join(getArboristPackagePath(), 'lib/override-set.js'),
     )
   }
   return _arboristOverrideSetClassPath