refactor(promise): rewrite promise bodies to async/await

Mechanically convert promise-returning function bodies to async/await:
resolve() returns the value directly, forwarding calls get .await, and
simple .then chains become await sequences. Also collapse the installer
double-Option (Result<Option<Option<PhpMixed>>> -> Result<Option<PhpMixed>>).

Hard spots that depend on the Loop::wait / job-machine boundary
(accept/reject orchestration, closures capturing &mut self, batch waits)
are left intact and marked with TODO(phase-c-promise) for manual porting.
The crate does not compile yet; traits still need #[async_trait].

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/crates/shirabe/src/downloader/perforce_downloader.rs b/crates/shirabe/src/downloader/perforce_downloader.rs
index ae433ef..fdb0f0d 100644
--- a/crates/shirabe/src/downloader/perforce_downloader.rs
+++ b/crates/shirabe/src/downloader/perforce_downloader.rs
@@ -40,7 +40,7 @@ impl PerforceDownloader {
         _url: String,
         _prev_package: Option<&dyn PackageInterface>,
     ) -> Result<Option<PhpMixed>> {
-        Ok(shirabe_external_packages::react::promise::resolve(None))
+        Ok(None)
     }
 
     pub async fn do_install(
@@ -70,7 +70,7 @@ impl PerforceDownloader {
             .sync_code_base(label.as_deref());
         self.perforce.as_mut().unwrap().cleanup_client_spec();
 
-        Ok(shirabe_external_packages::react::promise::resolve(None))
+        Ok(None)
     }
 
     fn get_label_from_source_reference(&self, source_ref: String) -> Option<String> {
@@ -118,7 +118,7 @@ impl PerforceDownloader {
         path: String,
         url: String,
     ) -> Result<Option<PhpMixed>> {
-        self.do_install(target, path, url)
+        self.do_install(target, path, url).await
     }
 
     pub fn get_local_changes(