feat: add RecipeEntry::related_files() for discovering associated files

Cargo.toml

@@ -21,6 +21,7 @@ cli = ["uniffi/cli"]
 [dependencies]
 camino = { version = "1.1", features = ["serde1"] }
 glob = "0.3"
+regex = "1"
 serde = { version = "1.0", features = ["derive"] }
 serde_yaml = "0.9"
 serde_json = "1.0"

docs/plans/2026-02-16-related-files-design.md

@@ -0,0 +1,80 @@
+# Design: `RecipeEntry::related_files()`
+
+## Summary
+
+Add a method to `RecipeEntry` that returns all filesystem paths related to a recipe: images (title + step) and recursively referenced recipe files.
+
+## Public API
+
+```rust
+impl RecipeEntry {
+    /// Returns all file paths related to this recipe.
+    ///
+    /// Includes:
+    /// - Title image (if any)
+    /// - Step/section images
+    /// - Referenced recipe .cook files (detected via @./path syntax)
+    /// - Recursively: related files of referenced recipes
+    ///
+    /// Returns an empty Vec for content-based recipes.
+    /// Missing referenced files are silently skipped.
+    /// Cycles are detected and broken automatically.
+    pub fn related_files(&self) -> Vec<Utf8PathBuf>
+}
+```
+
+## Internal Design
+
+### Helper function
+
+```rust
+fn collect_related_files(
+    path: &Utf8Path,
+    visited: &mut HashSet<Utf8PathBuf>,
+    result: &mut Vec<Utf8PathBuf>,
+)
+```
+
+### Algorithm
+
+1. Add recipe path to `visited` set (prevents cycles)
+2. Find title image via `find_title_image()` — add to result if found
+3. Find step images via `find_step_images()` — add all paths to result
+4. Read recipe content, extract `@./path` references via regex
+5. For each referenced recipe:
+   - Resolve path relative to current recipe's directory
+   - Try `.cook` extension if not specified
+   - If file exists and not in `visited`: add to result, recurse
+
+### Regex for recipe references
+
+Pattern: `@([./][^{}\s]+)` — captures path after `@` starting with `./`, stopping at whitespace or `{`.
+
+### No caching
+
+The method returns a fresh `Vec` each call. Caching doesn't fit well with:
+- Recursive traversal needing mutable `visited` state
+- File system state that can change between calls
+
+## Edge Cases
+
+- **Content-based recipes** (`RecipeSource::Content`): return empty `Vec`
+- **Missing referenced files**: silently skip
+- **Circular references**: `visited` set prevents infinite recursion
+- **Deduplication**: `visited` set deduplicates across branches
+
+## FFI
+
+Add to `FfiRecipeEntry`:
+
+```rust
+fn related_files(&self) -> Vec<String>
+```
+
+## Decisions
+
+- **Regex over parser**: lightweight, no new dependencies, sufficient for `@./path` pattern
+- **No caching**: simpler recursion, avoids stale filesystem data
+- **Method on RecipeEntry**: consistent with existing API (`title_image()`, `step_images()`)
+- **Flat Vec<Utf8PathBuf>**: simple to consume, deduplicated
+- **Recursive**: follows referenced recipes to collect their files too