Run executables directly (#645)

- Apps can be launched directly from file paths (including Files app support)
- Added executable detection to identify unsupported or invalid binaries before launch.
- App startup is now streamlined through separate registered-app and direct-execution interfaces.
- Existing app launch points were migrated to the updated startup APIs.

Modules/app-module/source/start.cpp

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: Apache-2.0
+#include <app/start.h>
+
+#include <app/private/ledger.h>
+#include <app/private/manager_internal.h>
+
+#include <tactility/concurrent/mutex.h>
+
+namespace {
+
+// Looks @a id up in the manifest registry, then delegates to app_manager_start_internal(). The
+// only path that requires a registered manifest; app_execute*() (app/execute.h) bypasses this
+// entirely.
+error_t start_internal_by_id(const char* id, AppInstanceId parent_instance_id, int argc, const char* const argv[], const AppStreamBinding* bindings, size_t binding_count, AppInstanceId* out_app_instance_id) {
+    auto& ledger = app_ledger();
+
+    mutex_lock(&ledger.mutex);
+    auto manifest_iterator = ledger.manifests.find(id);
+    if (manifest_iterator == ledger.manifests.end()) {
+        mutex_unlock(&ledger.mutex);
+        return ERROR_NOT_FOUND;
+    }
+    const AppManifest* manifest = manifest_iterator->second;
+    mutex_unlock(&ledger.mutex);
+
+    return app_manager_start_internal(manifest, manifest->location, manifest->stack, parent_instance_id, argc, argv, bindings, binding_count, out_app_instance_id);
+}
+
+} // namespace
+
+extern "C" {
+
+error_t app_start(const char* id, int argc, const char* const argv[], AppInstanceId* out_app_instance_id) {
+    return start_internal_by_id(id, 0, argc, argv, nullptr, 0, out_app_instance_id);
+}
+
+error_t app_start_for_result(const char* id, int argc, const char* const argv[], AppInstanceId parent_instance_id, AppInstanceId* out_app_instance_id) {
+    return start_internal_by_id(id, parent_instance_id, argc, argv, nullptr, 0, out_app_instance_id);
+}
+
+error_t app_start_with_streams(const char* id, const AppStreamBinding* bindings, size_t binding_count, AppInstanceId* out_app_instance_id) {
+    return start_internal_by_id(id, 0, 0, nullptr, bindings, binding_count, out_app_instance_id);
+}
+
+error_t app_start_for_result_with_streams(const char* id, int argc, const char* const argv[], const AppStreamBinding* bindings, size_t binding_count, AppInstanceId parent_instance_id, AppInstanceId* out_app_instance_id) {
+    return start_internal_by_id(id, parent_instance_id, argc, argv, bindings, binding_count, out_app_instance_id);
+}
+
+} // extern "C"