update links under the root README file

05-filesystems-packaging/13-iofs-config-loader/README.md

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+# Kata 13: The Filesystem-Agnostic Config Loader
+**Target Idioms:** `io/fs` abstraction, `fs.WalkDir`, Testability via `fstest.MapFS`, `embed` readiness  
+**Difficulty:** 🟡 Intermediate
+
+## 🧠 The "Why"
+In Go, passing `"/etc/app/config"` all over the place hard-couples your logic to the OS.
+Idiomatic Go uses `fs.FS` so you can:
+- load from disk,
+- load from embedded files,
+- load from a ZIP filesystem,
+- unit test without touching the real filesystem.
+
+## 🎯 The Scenario
+Your CLI loads configuration fragments from a directory tree, merges them, and prints a final config report.
+
+## 🛠 The Challenge
+Implement:
+- `func LoadConfigs(fsys fs.FS, root string) (map[string][]byte, error)`
+
+### 1. Functional Requirements
+- [ ] Walk `root` recursively and read all `*.conf` files.
+- [ ] Return a map of `path -> content`.
+- [ ] Reject invalid paths cleanly.
+
+### 2. The "Idiomatic" Constraints (Pass/Fail Criteria)
+- [ ] **Must** accept `fs.FS` (not `os` paths) in the core API.
+- [ ] **Must** use `fs.WalkDir` and `fs.ReadFile`.
+- [ ] **Must NOT** use `os.Open` / `filepath.Walk` inside the core loader.
+- [ ] Unit tests must use `testing/fstest.MapFS`.
+
+## 🧪 Self-Correction (Test Yourself)
+- **If you can’t test without real files:** you failed.
+- **If your loader only works on disk:** you failed the abstraction goal.
+
+## 📚 Resources
+- https://pkg.go.dev/io/fs
+- https://go.dev/src/embed/embed.go