fix(ast-grep): add isValidBinary check to all path resolutions

- Check file size >10KB to filter out placeholder files
- Check cached binary first
- Then npm package paths with validation
- Homebrew paths as last resort
- Fixes SIGTRAP/ENOEXEC from invalid binaries

src/tools/ast-grep/constants.ts

@@ -1,6 +1,10 @@
+import { createRequire } from "module"
+import { dirname, join } from "path"
 import { existsSync, statSync } from "fs"
 import { getCachedBinaryPath } from "./downloader"
 
+type Platform = "darwin" | "linux" | "win32" | "unsupported"
+
 function isValidBinary(filePath: string): boolean {
   try {
     return statSync(filePath).size > 10000
@@ -9,12 +13,70 @@ function isValidBinary(filePath: string): boolean {
   }
 }
 
+function getPlatformPackageName(): string | null {
+  const platform = process.platform as Platform
+  const arch = process.arch
+
+  const platformMap: Record<string, string> = {
+    "darwin-arm64": "@ast-grep/cli-darwin-arm64",
+    "darwin-x64": "@ast-grep/cli-darwin-x64",
+    "linux-arm64": "@ast-grep/cli-linux-arm64-gnu",
+    "linux-x64": "@ast-grep/cli-linux-x64-gnu",
+    "win32-x64": "@ast-grep/cli-win32-x64-msvc",
+    "win32-arm64": "@ast-grep/cli-win32-arm64-msvc",
+    "win32-ia32": "@ast-grep/cli-win32-ia32-msvc",
+  }
+
+  return platformMap[`${platform}-${arch}`] ?? null
+}
+
 export function findSgCliPathSync(): string | null {
+  const binaryName = process.platform === "win32" ? "sg.exe" : "sg"
+
   const cachedPath = getCachedBinaryPath()
   if (cachedPath && isValidBinary(cachedPath)) {
     return cachedPath
   }
 
+  try {
+    const require = createRequire(import.meta.url)
+    const cliPkgPath = require.resolve("@ast-grep/cli/package.json")
+    const cliDir = dirname(cliPkgPath)
+    const sgPath = join(cliDir, binaryName)
+
+    if (existsSync(sgPath) && isValidBinary(sgPath)) {
+      return sgPath
+    }
+  } catch {
+    // @ast-grep/cli not installed
+  }
+
+  const platformPkg = getPlatformPackageName()
+  if (platformPkg) {
+    try {
+      const require = createRequire(import.meta.url)
+      const pkgPath = require.resolve(`${platformPkg}/package.json`)
+      const pkgDir = dirname(pkgPath)
+      const astGrepName = process.platform === "win32" ? "ast-grep.exe" : "ast-grep"
+      const binaryPath = join(pkgDir, astGrepName)
+
+      if (existsSync(binaryPath) && isValidBinary(binaryPath)) {
+        return binaryPath
+      }
+    } catch {
+      // Platform-specific package not installed
+    }
+  }
+
+  if (process.platform === "darwin") {
+    const homebrewPaths = ["/opt/homebrew/bin/sg", "/usr/local/bin/sg"]
+    for (const path of homebrewPaths) {
+      if (existsSync(path) && isValidBinary(path)) {
+        return path
+      }
+    }
+  }
+
   return null
 }