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/shared/pty-rpc-schema.ts

@@ -146,6 +146,10 @@ export type PtyRPCRequests = {
       error?: string;
     };
   };
+  "files.ensureDir": {
+    params: { path: string };
+    response: { ok: boolean; path?: string; error?: string };
+  };
   /** Unguarded directory listing for PathBrowser (dirs only, no file content) */
   "files.browse": {
     params: { path: string };