feat(add-project): native folder picker (Finder) in the desktop app

desktop/main.js

@@ -7,7 +7,7 @@
 // answers, then points a BrowserWindow at it.
 'use strict';
 
-const { app, BrowserWindow, shell, dialog, Menu } = require('electron');
+const { app, BrowserWindow, shell, dialog, Menu, ipcMain } = require('electron');
 const { spawn } = require('child_process');
 const http = require('http');
 const https = require('https');
@@ -120,15 +120,38 @@ function waitForServer(port, timeoutMs) {
   });
 }
 
+// Native folder picker for the "Add project" flow. Returns the chosen absolute
+// path, or null on cancel. Registered once (guarded) so re-creating the window
+// doesn't stack duplicate handlers.
+let _pickFolderRegistered = false;
+function registerIpc() {
+  if (_pickFolderRegistered) return;
+  _pickFolderRegistered = true;
+  ipcMain.handle('codbash:pick-folder', async function () {
+    const res = await dialog.showOpenDialog(win, {
+      title: 'Choose a project folder',
+      properties: ['openDirectory', 'createDirectory'],
+    });
+    if (res.canceled || !res.filePaths || !res.filePaths.length) return null;
+    return res.filePaths[0];
+  });
+}
+
 async function createWindow() {
+  registerIpc();
   win = new BrowserWindow({
     width: 1320,
     height: 860,
     minWidth: 920,
     minHeight: 600,
     title: 'codbash',
     backgroundColor: '#0b0d12',
-    webPreferences: { contextIsolation: true, nodeIntegration: false, spellcheck: false },
+    webPreferences: {
+      contextIsolation: true,
+      nodeIntegration: false,
+      spellcheck: false,
+      preload: path.join(__dirname, 'preload.js'),
+    },
   });
 
   // http/https links open in the user's real browser, not inside the app.

desktop/preload.js

@@ -0,0 +1,12 @@
+'use strict';
+
+// Minimal, safe bridge exposed to the loaded dashboard page. contextIsolation
+// is on and nodeIntegration off, so the renderer only sees exactly what we
+// expose here — a single method that opens the native folder picker.
+const { contextBridge, ipcRenderer } = require('electron');
+
+contextBridge.exposeInMainWorld('codbashDesktop', {
+  isDesktop: true,
+  // Resolves to the chosen absolute folder path, or null if the user cancels.
+  pickFolder: () => ipcRenderer.invoke('codbash:pick-folder'),
+});

src/frontend/app.js

@@ -4085,9 +4085,26 @@ function openAddProject() {
   var input = document.getElementById('apLocalPath');
   if (input) { input.value = ''; setTimeout(function() { input.focus(); }, 50); }
   var err = document.getElementById('apLocalError'); if (err) err.textContent = '';
+  // Desktop app only: reveal the native "Browse…" folder picker (the browser
+  // has no way to open a Finder folder dialog and return an absolute path).
+  var browse = document.getElementById('apBrowseBtn');
+  if (browse) browse.style.display =
+    (window.codbashDesktop && typeof window.codbashDesktop.pickFolder === 'function') ? '' : 'none';
   _installModalFocusTrap(overlay);
 }
 
+// Open the OS folder picker (Finder) in the desktop app and drop the chosen
+// absolute path into the input. No-op in the browser (button stays hidden).
+function browseForProjectFolder() {
+  if (!(window.codbashDesktop && typeof window.codbashDesktop.pickFolder === 'function')) return;
+  window.codbashDesktop.pickFolder().then(function (dir) {
+    if (!dir) return;
+    var input = document.getElementById('apLocalPath');
+    if (input) { input.value = dir; input.focus(); }
+    var err = document.getElementById('apLocalError'); if (err) err.textContent = '';
+  }).catch(function () {});
+}
+
 function closeAddProject() {
   var overlay = document.getElementById('addProjectOverlay');
   if (overlay) {

src/frontend/index.html

@@ -300,9 +300,12 @@ <h3 id="apTitle">Add project</h3>
         <div class="ap-body">
             <div class="ap-pane" id="apPaneLocal" role="tabpanel">
                 <label for="apLocalPath">Folder path on this machine</label>
-                <input type="text" id="apLocalPath" placeholder="/Users/me/code/my-project" autocomplete="off" aria-describedby="apLocalHint" list="apPathSuggestions" />
+                <div class="ap-path-row">
+                    <input type="text" id="apLocalPath" placeholder="/Users/me/code/my-project" autocomplete="off" aria-describedby="apLocalHint" list="apPathSuggestions" />
+                    <button type="button" id="apBrowseBtn" class="toolbar-btn" style="display:none" onclick="browseForProjectFolder()" title="Choose a folder…">Browse…</button>
+                </div>
                 <datalist id="apPathSuggestions"></datalist>
-                <div class="ap-hint" id="apLocalHint">Start typing to pick from your known project folders. <code>~</code> is expanded.</div>
+                <div class="ap-hint" id="apLocalHint">Start typing to pick from your known project folders, or <strong>Browse…</strong> in the desktop app. <code>~</code> is expanded.</div>
                 <div class="ap-error" id="apLocalError" role="alert"></div>
             </div>
             <div class="ap-pane" id="apPaneOwned" style="display:none" role="tabpanel">

src/frontend/styles.css

@@ -1086,6 +1086,9 @@ body[data-view="overview"] .toolbar { display: none; }
     color: var(--text-primary);
     font-size: 13px;
 }
+.ap-path-row { display: flex; gap: 8px; align-items: stretch; }
+.ap-path-row input[type="text"] { flex: 1; }
+.ap-path-row #apBrowseBtn { flex: 0 0 auto; white-space: nowrap; }
 .ap-hint { font-size: 11px; color: var(--text-muted); margin-top: 6px; }
 .ap-error { font-size: 12px; color: var(--accent-red); margin-top: 8px; min-height: 18px; }
 .ap-filter { margin-bottom: 8px; }