Consolidate JKHL candidate state behavior into single enum setting

[Copilot]

Replaces two boolean settings (kUseJKtoMoveCompositorCursorInCandidateState, kUseHLtoMoveCompositorCursorInCandidateState) with a single integer enum kCandidateStateJKHLBehavior offering three mutually exclusive behaviors:

• 0: Unassigned (default) - JKHL remain as candidate selection keys
• 1: JK moves composition buffer cursor; HL flips candidate row/column
• 2: HL moves composition buffer cursor; JK flips candidate row/column

Changes

Core Settings Layer

• Added kCandidateStateJKHLBehavior to UserDef enum with integer dataType
• Updated PrefMgrProtocol and PrefMgr with new property (default: 0)
• Added validation in fixOddPreferencesCore() to constrain values to [0,1,2]
• Removed deprecated boolean properties from all preference layers

Input Handling

InputHandler_HandleCandidate.swift: Replaced boolean checks with enum comparisons:

let allowMovingCursorByJK = allowMovingCompositorCursor && prefs.candidateStateJKHLBehavior == 1
let allowMovingCursorByHL = allowMovingCompositorCursor && prefs.candidateStateJKHLBehavior == 2

InputSession_HandleEvent.swift: Added row-flipping key translation. When in candidate state, dynamically converts JKHL to arrow keys based on window orientation:

// Converts J→Down/Right, K→Up/Left, H→Left/Up, L→Right/Down
// Orientation-aware: adjusts based on isVerticalCandidateWindow

UI Updates

• SwiftUI Settings: Renders as RadioGroupPickerStyle dropdown with three options
• AppKit Settings: Added to candidate settings tab with sanity check callback
• Updated candidate key validator to exclude JK (behavior=1) or HL (behavior=2) from selection keys

Localization

Added i18n keys for en/ja/zh-Hans/zh-Hant:

• kCandidateStateJKHLBehavior.shortTitle: "JKHL key behavior in candidate window"
• kCandidateStateJKHLBehavior.description: Warning about auto-exclusion from candidate keys and %quick compatibility
• kCandidateStateJKHLBehavior.option.{0,1,2}: Per-option descriptions

Removed deprecated localization keys for the two boolean settings.

Technical Notes

The row-flipping logic sits in SessionProtocol (not InputHandlerProtocol) to maintain code independence and avoid structural similarities with external implementations per issue requirements.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feature] +UserDef.kCandidateStateJKHLBehavior and +PrefMgrProtocol.candidateStateJKHLBehavior.</issue_title>
<issue_description>

任務目標

將 UserDef 與 PrefMgr 對應的 kUseJKtoMoveCompositorCursorInCandidateState 和 kUseHLtoMoveCompositorCursorInCandidateState 這兩個選項的行為做整合、以 kCandidateStateJKHLBehavior 取而代之。

// SPECIAL NOTICE TO COPILOT:

ENSURE YOUR IMPLEMENTATION IS DIFFERENT FROM `https://github.com/openvanilla/McBopomofo/pull/708`.

EVERY PLAGIARISM-LEVEL SIMILARITY WILL BRING DEVASTATING RISK OF BEING DEFAMED BY BAD-INTENTION-DRIVEN INDIVIDUALS.

(This notice will be referred as `code-similarity-concerns` in the rest of this article.)

具體施工方案：

Step 1: UserDefaults & UserDef

UserDef 新增 case kCandidateStateJKHLBehavior 且 rawValue 是 CandidateStateJKHLBehavior。

    case .kCandidateStateJKHLBehavior: return .init(
        userDef: self, shortTitle: "i18n:UserDef.kCandidateStateJKHLBehavior.shortTitle",
        description: "i18n:UserDef.kCandidateStateJKHLBehavior.description",
        options: [
          0: "i18n:UserDef.kCandidateStateJKHLBehavior.option.0",
          1: "i18n:UserDef.kCandidateStateJKHLBehavior.option.1",
          2: "i18n:UserDef.kCandidateStateJKHLBehavior.option.2",
        ]
      )

Data type of case kCandidateStateJKHLBehavior: Integer.

Since we provide 3 options for this case, the actual UI of this UserPref in Settings Window (both SwiftUI and AppKit) will be rendered as a dropdown menu.

English Localization (you may ameliorate its expression):

"i18n:UserDef.kCandidateStateJKHLBehavior.shortTitle" = "JKHL key behavior in candidate window:";
"i18n:UserDef.kCandidateStateJKHLBehavior.description" = "⚠︎ Regarding these specific composition-buffer-cursor-flipping-keys: 1) This will automatically prevent them to be used as candidate keys; 2) They won't work with ‘%quick’ candidates in cassette mode.";
"i18n:UserDef.kCandidateStateJKHLBehavior.option.0" = "Unassigned";
"i18n:UserDef.kCandidateStateJKHLBehavior.option.1" = "JK to move cursor in the composition buffer; HL to flip current row / column";
"i18n:UserDef.kCandidateStateJKHLBehavior.option.2" = "HL to move cursor in the composition buffer; JK to flip current row / column";

flip current row / column is the action in the candidate window determining which candidate is the currently-highlighted one. The JK/HL keys set for this purposes will be referred as "row-flipping-keys" in the rest of this article.

Finish all other translations in JP, zh-Hans, and zh-Hant-TW. Here's the term table (separated by TAB char):

TERM	JP	zh-Hans	zhHant-TW
Composition Buffer	入力緩衝列	組字区	組字區
Candidate Window	候補陳列ウィンドウ	选字窗	選字窗

(After Step 2 you may remove kUseJKtoMoveCompositorCursorInCandidateState & kUseHLtoMoveCompositorCursorInCandidateState from UserDef.)

Step 2: PrefMgrProtocol and PrefMgr:

1. Remove useJKtoMoveCompositorCursorInCandidateState and useHLtoMoveCompositorCursorInCandidateState.
2. Add candidateStateJKHLBehavior binded to kCandidateStateJKHLBehavior with default value 0.

Step 3: InputHandlerProtocol surgery -- Fix the affected bindings regarding changes in Step 2.

• The "JK / HL to move composition-buffer-cursor" feature only needs to change their prefs bindings to the new prefs.candidateStateJKHLBehavior one.

Step 4: SessionProtocol tweaks:

• Regarding the row-flipping-keys: In the InputSession_HandleEvent.swift file around the blank line at line 149 you add a new processing step: If state.isCandidateContainer, then use eventToDeal.reinitiate to try retranslate the row-flipping-keys to the correct arrow key (depending on whether the actual candidate window layout is line-as-row or line-as-column).

  • Regarding why we don't put this in InputHandlerProtocol.handleCandidate(: This reduces the risks of the above-mentioned code-similarity-concerns.

• You may add unit tests of this PR against MainAssembly if you wish.

Step 4:

Fix the Settings UI (both SwiftUI and AppKit version).

(Your response language in this dialog will always be `zh-Hant-TW.)</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature] +UserDef.kCandidateStateJKHLBehavior and +PrefMgrProtocol.candidateStateJKHLBehavior. #564

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