feat(ui): #25 Phase K.3 — Settings panel + click-to-rebind + Phase K shipped

Phase K final commit. Settings panel with click-to-rebind UX on top of
the K.1+K.2 input architecture, plus the roadmap / ISSUES / memory
updates that retire Phase K.

InputDispatcher gains BeginCapture / CancelCapture / IsCapturing /
SetBindings — modal capture suppresses normal action firing for the
next chord. Esc cancels (returns sentinel default chord); modifier-only
keys don't complete capture; non-modifier key down with current
modifier mask completes.

IPanelRenderer + ImGuiPanelRenderer + FakePanelRenderer gain
BeginMainMenuBar / EndMainMenuBar / BeginMenu / EndMenu / MenuItem
primitives.

SettingsVM owns a draft copy of KeyBindings with explicit Save /
Cancel / Reset semantics. Click-to-rebind enters dispatcher capture
mode; on chord captured, conflict-detect against draft (excluding the
action being rebound itself); surface a ConflictPrompt when the chord
collides; ResolveConflict(replace=true|false) commits or reverts.
ResetActionToDefault restores a single action to RetailDefaults();
ResetAllToDefaults rebuilds the entire draft. Save invokes the
onSave callback (which writes JSON + swaps the live dispatcher's
bindings).

SettingsPanel renders 8 retail-keymap-categorized CollapsingHeader
sections (Movement, Postures, Camera, Combat, UI panels, Chat,
Hotbar, Emotes). Per action: name + current binding(s) summary +
"Rebind"/"Reset" buttons. Conflict prompt at the top when pending.
Save / Cancel / "Reset all to retail defaults" at the top.

GameWindow registers SettingsPanel + wires F11 →
ToggleOptionsPanel → IsVisible toggle, plus a top-of-frame ImGui
MainMenuBar with View → Settings/Vitals/Chat/Debug entries (calls
ImGui directly — the abstraction methods exist for backend
portability but the host doesn't own a menu-bar surface).

Tests: +37 across InputDispatcherCaptureTests (7),
IPanelRendererMainMenuBarTests (9), SettingsVMTests (13),
SettingsPanelTests (8). Solution total 1220 green.

Roadmap (docs/plans/2026-04-11-roadmap.md) appends Phase K shipped
section after Phase J with K.1a–K.3 commit SHAs. ISSUES.md files
Phase L deferred work as #L.1–#L.8 (hotbar UI, spellbook favorites,
combat-mode dispatch, F-key panels, floating chat windows, UI layout
save/load, joystick bindings, plugin input subscription) and adds
#21–#25 to Recently closed. project_input_pipeline.md updated to
shipped state. CLAUDE.md gets an input-pipeline reference.

Closes Phase K.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.UI.Abstractions/IPanelRenderer.cs

@@ -206,4 +206,33 @@ public interface IPanelRenderer
     /// typing without clicking the field.
     /// </summary>
     void SetKeyboardFocusHere();
+
+    // -- Phase K.3 — top-of-screen main menu bar -------------------------
+
+    /// <summary>
+    /// Open the top-of-screen main menu bar. Returns true if the bar is
+    /// visible (top-level menus go inside that branch). Always pair with
+    /// <see cref="EndMainMenuBar"/> when the call returned true.
+    /// </summary>
+    bool BeginMainMenuBar();
+
+    /// <summary>Close the menu bar opened by <see cref="BeginMainMenuBar"/>.</summary>
+    void EndMainMenuBar();
+
+    /// <summary>
+    /// Open a top-level menu within a menu bar. Returns true if the menu
+    /// is open — the caller emits <see cref="MenuItem"/> entries inside
+    /// that branch, then calls <see cref="EndMenu"/>.
+    /// </summary>
+    bool BeginMenu(string label);
+
+    /// <summary>Close the menu opened by <see cref="BeginMenu"/>.</summary>
+    void EndMenu();
+
+    /// <summary>
+    /// A clickable menu item with optional shortcut hint (e.g.
+    /// <c>"F11"</c>) drawn right-aligned. Returns true on the single
+    /// frame the user clicks the item; false otherwise.
+    /// </summary>
+    bool MenuItem(string label, string? shortcut = null);
 }