## ADDED Requirements

### Requirement: Hybrid storage layout
The system SHALL store media files under the app Documents `library/` directory and SHALL store catalog, session, and album metadata in SwiftData (not Core Data, and not JSON as the runtime source of truth).

#### Scenario: Imported file on disk and in catalog
- **WHEN** a media file is successfully imported
- **THEN** the file exists under Documents/`library/` at a stable relative path AND a SwiftData `CatalogEntry` records that relative path, kind, name, and import time

#### Scenario: No Core Data dependency
- **WHEN** the app persists metadata
- **THEN** persistence MUST use SwiftData APIs and MUST NOT require a Core Data stack

### Requirement: Directory listing and library mutations
The system SHALL list directories under `library/`, and SHALL support create folder, rename, move, and delete for library entries while keeping SwiftData catalog consistent.

#### Scenario: List subdirectory
- **WHEN** the user opens a relative directory in Explorer
- **THEN** the system returns folders and files in that directory, attaching catalog metadata for known media files

#### Scenario: Delete file removes catalog entry
- **WHEN** the user deletes a media file from the library
- **THEN** the file is removed from disk AND its `CatalogEntry` is removed or marked unavailable so it no longer appears as a playable resource

#### Scenario: Path escape rejected
- **WHEN** a mutation or import provides a relative path that would escape `library/`
- **THEN** the system MUST reject the operation

### Requirement: Resource kind from extension
The system SHALL classify imported files as `video`, `audio`, `pdf`, or `other` using extension rules aligned with the desktop StudyDeck classifier.

#### Scenario: Common media extensions
- **WHEN** files with extensions such as `mp4`, `mp3`, or `pdf` are imported
- **THEN** their catalog kind is `video`, `audio`, or `pdf` respectively

### Requirement: Session and album persistence
The system SHALL persist sessions (including progress fields and optional album linkage) and albums in SwiftData, including which session is active.

#### Scenario: Active session survives relaunch
- **WHEN** the user has an active session and force-quits then relaunches the app
- **THEN** the active session identity and last saved progress fields are available for resume