Refactor application path handling and data storage architecture

Replace simple directory-based path system with git-aware data management that uses global data directories and proper workspace detection.

🤖 Generated with opencode
Co-Authored-By: opencode <noreply@opencode.ai>

packages/opencode/src/util/filesystem.ts

@@ -0,0 +1,18 @@
+import { exists } from "fs/promises"
+import { dirname, join } from "path"
+
+export namespace Filesystem {
+  export async function findUp(target: string, start: string) {
+    let currentDir = start
+    while (true) {
+      const targetPath = join(currentDir, target)
+      if (await exists(targetPath)) return targetPath
+      const parentDir = dirname(currentDir)
+      if (parentDir === currentDir) {
+        return
+      }
+      currentDir = parentDir
+    }
+  }
+}
+