Add a preference

A setting is a multi-file contract keyed on one string. Follow every step that applies; skipping one produces a setting that silently fails to persist, export, or apply on the hot path.

1. Declare the key and property

In BetterCmdTab/App/Preferences.swift:

• Add the key to the Keys enum as "Switcher.camelCaseName". The string is the contract — it is read by name in other files, exported to config files, and never renamed after shipping.
• Add a @Published property whose didSet persists to UserDefaults, and load it in init and in reloadFromDefaults() (settings import and config-file sync call this — a property missing there ignores imports). Copy the exact pattern of an adjacent property of the same type.
• Clamped ints get a static let …Range: ClosedRange<Int> next to the other range constants, and clamp on read.

Complete when: the property round-trips through reloadFromDefaults().

2. Wire the hot path, if any

If the value is read while the switcher opens or cycles (CatalogFilter, SwitcherController, WindowEnumerator, Activator, HotkeyTap, RecentlyClosedStore), those consumers read the key string directly from UserDefaults.standard off the main actor — never touch Preferences.shared there. Match the existing direct-read sites in the file you are editing.

Complete when: no hot-path code awaits the main actor to read the value.

3. Per-shortcut override, if applicable

If the setting should be overridable per shortcut (#74), extend ShortcutOverride in Preferences.swift: add the optional field, its dictionary encoding, the init?(dictionary:) decode, and the entry in knownKeys (an omitted knownKeys entry makes the field bounce into passthrough and never apply). Then resolve it where the other overrides resolve into CatalogFilter.Config / reveal-time reads.

Complete when: the field survives a dictionary → init?(dictionary:) round trip and is absent from passthrough.

4. Portability and config file — usually free

Export/import (SettingsPortability.swift) and ~/.config/bettercmdtab/config.json (ConfigFile.swift) pick up any Switcher.* key automatically. Only act if the value is device-local state (caches, recently-closed, machine-specific paths): add it to exportExcludedKeys in SettingsPortability.swift.

5. UI and strings

Add the control to the matching pane view controller in BetterCmdTab/Settings/ (fragile or new behavior goes behind the off-by-default Experimental pane). Register the control in SettingsCatalog.swift if the pane search should find it. All labels use String(localized:) — then follow the localize-strings skill for the catalog entries.

6. Verify

New pure-logic behavior gets a Swift Testing test. Then run the suites the contract touches:

xcodebuild -scheme "BetterCmdTab Debug" -destination 'platform=macOS' test \
  -only-testing:BetterCmdTabTests/PreferencesEnumTests \
  -only-testing:BetterCmdTabTests/SettingsPortabilityTests \
  -only-testing:BetterCmdTabTests/LocalizationCatalogTests

Complete when: those suites pass and the setting survives an export → import round trip.