ship prebuilt ptyc in native/linux-x64/

Prebuilt ptyc binary sits alongside libtree-sitter.so in the
platform-specific native directory. Resolution order:
native/linux-x64/ptyc → ptyc/bin/ptyc → ~/.local/bin/ptyc → PATH.
Eliminates the make ptyc-build step on fresh clones.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/main.dart

@@ -154,6 +154,7 @@ Future<List<ThemeDefinition>> _loadBundledThemes() async {
 /// catalogs load lazily on activate in later tiers.
 String _resolvePtyc(String repoRoot) {
   final candidates = [
+    '$repoRoot/native/linux-x64/ptyc',
     '$repoRoot/ptyc/bin/ptyc',
     '${Platform.environment['HOME']}/.local/bin/ptyc',
     'ptyc',