Add app-specific shortcuts with optional when filters

[rahulxsomething]

Summary

• Adds optional when field to actions and groups with includeApps/excludeApps bundle ID arrays
• The same key can map differently depending on the frontmost app (e.g., t → Terminal globally, t → Google in Chrome)
• Entire groups can be scoped to specific apps
• "Everywhere except X" patterns supported via excludeApps
• Configs without when fields behave identically to before (fully backward compatible)

Config example

{
  "key": "a",
  "type": "command",
  "value": "chrome-action",
  "when": {
    "includeApps": ["com.google.Chrome"],
    "excludeApps": ["com.google.Chrome.canary"]
  }
}

Precedence tiers

Tier	Condition	Priority
A	includeApps matches frontmost app	Highest
B	excludeApps non-empty, includeApps empty	Middle
C	No when / both arrays empty	Lowest (global)

Changes

File	Change
Leader Key/UserConfig.swift	When struct; when on Action, Group, ActionOrGroup, Item
Leader Key/AppFilter.swift	New — matching, tier computation, resolution
Leader Key/Controller.swift	Capture frontmost app in show(), resolve in handleKey()
Leader Key/UserState.swift	frontmostBundleID property
Leader Key/Cheatsheet.swift	Filter cheatsheet display by app
Leader Key/ConfigValidator.swift	Tier-aware duplicate validation, when self-consistency checks
Tests	28 new tests across 3 test files

Test plan

• All 69 tests pass (0 failures)
• Tier A override: Chrome-specific key fires in Chrome, global fires elsewhere
• Tier B exclude: item hidden for excluded app, visible for others
• App-scoped group: group hidden for non-matching apps
• Cheatsheet reflects app-specific filtering
• Backward compatibility: configs without when work identically

🤖 Generated with Claude Code