Refactor: extract key-capture accept/translate rules into KeyCaptureRules

[GamalAnwar]

Summary

Slice 2 of 2. Both single-flight key captures — ShortcutCapture (global hotkeys) and EditorKeyCapture (editor tool rebinding) — embedded their pure accept/translate decisions inside the NSEvent monitor closures, where they were untestable. This lifts the decisions out:

HotKeyCaptureRule.combination(keyCode:modifiers:)  // nil unless ≥1 device-independent modifier
EditorToolKey.binding(char:modifiers:)             // lowercase, validate charset, ⇧-prefix iff Shift-only

The monitor closures now read as control-flow only:

// ShortcutCapture
guard let combo = HotKeyCaptureRule.combination(keyCode: event.keyCode,
                                                modifiers: event.modifierFlags) else { return nil }
// EditorKeyCapture
guard let raw = event.charactersIgnoringModifiers,
      let key = EditorToolKey.binding(char: raw, modifiers: event.modifierFlags) else { return nil }

Scope / safety

• Behavior-preserving. Same modifier-required rule, same charset, same mods == .shift exact-match for the ⇧ prefix, same .deviceIndependentFlagsMask intersection.
• The single-flight mechanism (static active, cancelActive, monitor add/remove, Esc-cancel, flagsChanged ignore) is deliberately left in place — it's inherently NSEvent-coupled and not unit-testable. Only the pure rules moved.

Tests

KeyCaptureRulesTests (10 cases): plain letter, lowercasing, ⇧-prefix on Shift, no prefix for Command, Shift+other not treated as Shift, valid symbol/digit, empty/space rejected; and for hotkeys: modifier required, keyCode+modifiers preserved, non-device-independent bits stripped.

Note

This is independent of #10 (thumbnail geometry) — different files, both branched off master. They can merge in any order.

🤖 Generated with Claude Code

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