feat(core): add embedded v2 session runtime and tool foundation (#30632)

packages/opencode/src/util/filesystem.ts

@@ -1,10 +1,11 @@
 import { chmod, mkdir, readFile, stat as statFile, writeFile } from "fs/promises"
 import { createWriteStream, existsSync, statSync } from "fs"
 import { realpathSync } from "fs"
-import { dirname, isAbsolute, join, relative, resolve as pathResolve, win32 } from "path"
+import { dirname, isAbsolute, join, resolve as pathResolve, win32 } from "path"
 import { Readable } from "stream"
 import { pipeline } from "stream/promises"
 import { Glob } from "@opencode-ai/core/util/glob"
+import { FSUtil } from "@opencode-ai/core/fs-util"
 import { fileURLToPath } from "url"
 
 // Fast sync version for metadata checks
@@ -163,13 +164,11 @@ export function windowsPath(p: string): string {
   )
 }
 export function overlaps(a: string, b: string) {
-  const relA = relative(a, b)
-  const relB = relative(b, a)
-  return !relA || !relA.startsWith("..") || !relB || !relB.startsWith("..")
+  return FSUtil.overlaps(a, b)
 }
 
 export function contains(parent: string, child: string) {
-  return !relative(parent, child).startsWith("..")
+  return FSUtil.contains(parent, child)
 }
 
 export async function findUp(