fix: harden isTestoFile against stale stubs and out-of-content files

The original report showed an "Outdated stub in index" exception
triggered by isTestoFile() called on a stale PsiFile from vendor/ -
where the physical file was already deleted but the VFS hadn't
refreshed yet, so virtualFile.isValid still returned true.

A bare isValid check is therefore not enough. To make isTestoFile()
robust:

- Skip files outside project content (ProjectFileIndex.isInContent),
  excluded folders and IDE-ignored paths - this filters out vendor/
  and similar locations before any PSI traversal happens, removing
  the root cause for the reported case.
- Wrap the AST-loading traversal in a try/catch that rethrows
  ProcessCanceledException and downgrades any other Throwable
  (including StubTreeAndIndexUnmatchCoarseException) to a logged
  warning + false, so a transient index inconsistency can no longer
  propagate as an unhandled exception through callers (live
  templates, inspection suppressor, run config producer, etc.).

Author: claude

src/main/kotlin/com/github/xepozz/testo/mixin.kt

@@ -1,6 +1,9 @@
 package com.github.xepozz.testo
 
 import com.github.xepozz.testo.tests.TestoTestDescriptor
+import com.intellij.openapi.diagnostic.Logger
+import com.intellij.openapi.progress.ProcessCanceledException
+import com.intellij.openapi.roots.ProjectFileIndex
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiFile
 import com.intellij.psi.util.PsiTreeUtil
@@ -12,6 +15,8 @@ import com.jetbrains.php.lang.psi.elements.ClassReference
 import com.jetbrains.php.lang.psi.elements.NewExpression
 import com.jetbrains.php.lang.psi.elements.PhpClass
 
+private val LOG = Logger.getInstance("#com.github.xepozz.testo.mixin")
+
 fun PsiElement.isTestoExecutable() = isTestoFunction() || isTestoMethod() || isTestoBench()
 
 fun PsiElement.isTestoBench() = when(this) {
@@ -58,11 +63,24 @@ fun PsiFile.isTestoFile(): Boolean {
     if (this !is PhpFile) return false
     val vFile = virtualFile ?: return false
     if (!vFile.isValid) return false
-    return TestoTestDescriptor.isTestClassName(name.substringBeforeLast("."))
-        || isTestoClassFile()
-        || isTestoFunctionFile()
-        || isTestBenchFile()
-        || isTestoConfigFile()
+
+    val fileIndex = ProjectFileIndex.getInstance(project)
+    if (!fileIndex.isInContent(vFile)) return false
+    if (fileIndex.isExcluded(vFile)) return false
+    if (fileIndex.isUnderIgnored(vFile)) return false
+
+    return try {
+        TestoTestDescriptor.isTestClassName(name.substringBeforeLast("."))
+            || isTestoClassFile()
+            || isTestoFunctionFile()
+            || isTestBenchFile()
+            || isTestoConfigFile()
+    } catch (e: ProcessCanceledException) {
+        throw e
+    } catch (e: Throwable) {
+        LOG.warn("Failed to determine whether ${vFile.path} is a Testo file", e)
+        false
+    }
 }
 
 fun PhpFile.isTestoConfigFile() = PsiTreeUtil.findChildrenOfType(this, ClassReference::class.java)