feat(project): add project trust and restricted execution mode (#517)

Projects now open with a user-owned trust decision. The prompt offers Preview in Restricted Mode, Don't Open and Trust Project, with an optional trusted parent folder; preview is the default focus so Enter never grants trust.

Restricted projects keep browsing, editing, saving, search and highlighting. Project-controlled execution is denied by default in the backend: run, debug, build, tools, language servers, plugins and Git commands that could honour repository configuration. Trusting a project enables those paths without reopening it, and decisions can be revoked in Settings.

Terminals stay available when the user opens one, without project shell settings, environment or virtualenv activation. A shell prompt that runs git in the folder can still honour the repository's core.fsmonitor.

Fixes #462

src/features/plugins/index.ts

@@ -70,7 +70,7 @@ export function activate(): () => void {
     startPluginBridge(),
     // Dev plugins (`<project>/.openidea/plugins`) depend on the open project.
     useProject.subscribe((s, prev) => {
-      if (s.project?.root !== prev.project?.root) void refreshPlugins();
+      if (s.project?.root !== prev.project?.root || s.project?.trusted !== prev.project?.trusted) void refreshPlugins();
     }),
   ];
   void refreshPlugins();