fix: downloads are marked and keep their extension; Explorer files are refused

The desktop app writes the Mark-of-the-Web on each file it saves on Windows, as
a browser does. Bidirectional controls are reserved characters in a saved name
(portable-name.js and paths.sanitize_for_download, and again in the main
process), so a name cannot display one extension and carry another. The node
refuses uploads of files Windows Explorer acts on by itself: desktop.ini,
.lnk, .url, .scf, .library-ms, .searchConnector-ms (F-19).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/packages/meshbay-client/src/main.js b/packages/meshbay-client/src/main.js
index 236a285..52ca168 100644
--- a/packages/meshbay-client/src/main.js
+++ b/packages/meshbay-client/src/main.js
@@ -1160,8 +1160,24 @@ function registerBridge() {
     return { path: chosen, name: path.basename(chosen) };
   });
 
+  // The Mark-of-the-Web, as a browser leaves on every download: the file came
+  // from somebody else's machine, and Windows decides what that means —
+  // SmartScreen for a program, Protected View for a document. This application
+  // writes its files itself, so nothing else marks them. NTFS only; elsewhere
+  // there is no such stream, and nothing is lost by not having one.
+  function markFromInternet(file) {
+    if (process.platform !== 'win32') return;
+    try {
+      fs.writeFileSync(`${file}:Zone.Identifier`, '[ZoneTransfer]\r\nZoneId=3\r\n');
+    } catch { /* FAT, exFAT, a network share: no alternate data streams */ }
+  }
+
   handle('save:begin', async (_e, suggestedName, opts) => {
-    const wanted = path.basename(String(suggestedName || 'download'));
+    // Bidirectional controls replaced here as well as in the page
+    // (portable-name.js): "invoice\u202efdp.exe" would be saved, and listed by
+    // the file manager, as "invoiceexe.pdf".
+    const wanted = path.basename(String(suggestedName || 'download'))
+      .replace(/[\u061c\u200e\u200f\u202a-\u202e\u2066-\u2069]/g, '_');
     const chosen = chosenDownloadDir();
     let target = null;
 
@@ -1231,6 +1247,7 @@ function registerBridge() {
       console.error('[MeshBay] could not finalise download:', err.message);
       return false;
     }
+    markFromInternet(sink.path);
     completedPaths.set(String(id), sink.path);
     return true;
   });