chore(git): demote routine missing-repository probes

Public Git clients may request info/refs before a repository has arrived
locally during normal event and Git-data propagation. Logging that expected
negative lookup at WARN obscures actionable Git transport failures.

Demote only the HTTP handler's pre-spawn repository existence message to
DEBUG. The RepositoryNotFound response, request metrics, and internal Git
warnings remain unchanged.

This assumes the existing error response remains sufficient client-visible
feedback. Changing push metric semantics or suppressing invariant failures is
deliberately excluded.

Validated with:
- git diff --check
- nix develop -c cargo test --lib git::handlers (11 passed)

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Log routine Git `info/refs` requests for repositories not yet available
+  locally at DEBUG rather than WARN; this is expected during propagation.
+
 ### Fixed
 
 - Preserve purgatory and rejected-event recovery across abrupt termination.

src/git/handlers.rs

@@ -47,7 +47,7 @@ pub async fn handle_info_refs(
 
     // Check if repository exists
     if !repo_path.exists() {
-        warn!("Repository not found: {:?}", repo_path);
+        debug!("Repository not found: {:?}", repo_path);
         return Err(GitError::RepositoryNotFound);
     }