audio: expose replaceIR over the IPC bridge

Wire the native replaceIR(slotId, path, gain) through audio-bridge (ipcMain
handle) + preload, so renderers get feedBackDesktop.audio.replaceIR. Lets the
rig-builder cab room swap a cab's IRs in place instead of a full loadPreset +
param re-apply (that re-apply was the brief 'can't move the mic yet' lag).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/main/audio-bridge.ts

@@ -1080,6 +1080,10 @@ export function initAudioBridge(): void {
         return await audio?.loadIR(irPath) ?? -1;
     });
 
+    ipcMain.handle('audio:replaceIR', async (_event, slotId: number, irPath: string, gain?: number) => {
+        return await audio?.replaceIR(slotId, irPath, typeof gain === 'number' ? gain : -1) ?? false;
+    });
+
     ipcMain.handle('audio:removeProcessor', (_event, slotId: number) => {
         audio?.removeProcessor(slotId);
         vstSlotPaths.delete(slotId);

src/main/preload.ts

@@ -402,6 +402,8 @@ const feedBackDesktopApi = {
         loadVST: (pluginPath: string) => ipcRenderer.invoke('audio:loadVST', pluginPath),
         loadNAMModel: (modelPath: string) => ipcRenderer.invoke('audio:loadNAMModel', modelPath),
         loadIR: (irPath: string) => ipcRenderer.invoke('audio:loadIR', irPath),
+        replaceIR: (slotId: number, irPath: string, gain?: number) =>
+            ipcRenderer.invoke('audio:replaceIR', slotId, irPath, gain),
         removeProcessor: (slotId: number) => ipcRenderer.invoke('audio:removeProcessor', slotId),
         moveProcessor: (from: number, to: number) => ipcRenderer.invoke('audio:moveProcessor', from, to),
         setBypass: (slotId: number, bypassed: boolean) => ipcRenderer.invoke('audio:setBypass', slotId, bypassed),