fix: wire orphaned IPC channels, fix data-loss bug, print preview events, sidebar navigation

- Fix file.clearRecent sending IPC to main process instead of clearing openTabs
- Wire show-batch-converter, show-document-compare, open-header-footer-dialog IPC channels
- Add print preview event listeners (mc:print-preview, mc:print-preview-styled) in App.tsx
- Fix sidebar hidden bridge buttons toggling sidebar closed after scroll
- Update sidebar menu labels to match actual sections (Files, Outline, Git)
- Fix ipc.print to be an object with show/doPrint methods (was bare function)
- Update callers: ExportPdfDialog, pdf-export, PrintPreview
- Add 7 regression tests for all fixes
- Clean 2 obsolete snapshots
- Build Linux packages (deb, AppImage, snap) — 549 tests passing

src/renderer/lib/ipc.ts

@@ -83,8 +83,12 @@ export const ipc = {
     writeBuffer: (args: { path: string; buffer: Uint8Array }): Promise<IpcResult<void | ChannelMissing>> =>
       safeCall('file', 'writeBuffer', args),
   },
-  print: (args: { html: string }): Promise<IpcResult<void | ChannelMissing>> =>
-    safeCall('print', 'show', args),
+  print: {
+    show: (args: { html: string }): Promise<IpcResult<void | ChannelMissing>> =>
+      safeCall('print', 'show', args),
+    doPrint: (args: { withStyles?: boolean }): Promise<IpcResult<void | ChannelMissing>> =>
+      safeCall('print', 'doPrint', args),
+  },
   export: {
     pdf: (opts: PdfOptions): Promise<IpcResult<ExportResult | ChannelMissing>> =>
       safeCall('export', 'pdf', opts),