fix(electrobun): wizard fixes — native dialog, models, PathBrowser, ensureDir

- Native dialog: resolve to nearest existing parent dir, detect user cancel
  (exit code 1) vs actual error, add createIfMissing option
- Claude models: fallback to KNOWN_CLAUDE_MODELS (6 models) when API key
  unavailable. Adds Opus 4.6, Sonnet 4.6, Opus 4.5, Sonnet 4, Haiku 4.5,
  Sonnet 3.7. Live API paginated to limit=100.
- PathBrowser: Select button moved to sticky header (always visible).
  Current path shown compact in header with RTL ellipsis.
- files.ensureDir RPC: creates directory recursively before project creation
- files.ensureDir added to RPC schema

ui-electrobun/src/mainview/PathBrowser.svelte

@@ -125,10 +125,14 @@
 </script>
 
 <div class="path-browser">
-  <!-- Header -->
+  <!-- Header with Select always visible -->
   <div class="pb-header">
     <span class="pb-title">{t('wizard.step1.browse' as any)}</span>
-    <button class="pb-close" onclick={onClose} aria-label={t('common.close' as any)}>✕</button>
+    <div class="pb-header-actions">
+      <span class="pb-current-compact" title={currentPath}>{currentPath}</span>
+      <button class="pb-select-btn" onclick={confirmSelect}>Select</button>
+      <button class="pb-close" onclick={onClose} aria-label={t('common.close' as any)}>✕</button>
+    </div>
   </div>
 
   <!-- Shortcuts -->
@@ -172,10 +176,9 @@
     {/if}
   </div>
 
-  <!-- Footer: current path + select -->
+  <!-- Footer: current path (Select moved to header) -->
   <div class="pb-footer">
     <span class="pb-current" title={currentPath}>{currentPath}</span>
-    <button class="pb-select-btn" onclick={confirmSelect}>Select</button>
   </div>
 </div>
 
@@ -199,6 +202,25 @@
     justify-content: space-between;
     padding: 0.375rem 0.5rem;
     border-bottom: 1px solid var(--ctp-surface0);
+    position: sticky;
+    top: 0;
+    z-index: 2;
+    background: var(--ctp-mantle);
+  }
+  .pb-header-actions {
+    display: flex;
+    align-items: center;
+    gap: 0.375rem;
+  }
+  .pb-current-compact {
+    font-size: 0.6875rem;
+    color: var(--ctp-subtext0);
+    max-width: 12rem;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+    direction: rtl;
+    text-align: left;
   }
 
   .pb-title { font-size: 0.75rem; font-weight: 600; color: var(--ctp-text); }