style: cargo fmt --all — make codebase rustfmt-clean

First run of the build-and-test CI gate (cargo fmt --all -- --check) surfaced
pre-existing formatting drift across the agent and server crates. Apply rustfmt
across the workspace so the codebase meets its own CI gate. Pure formatting; no
logic changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

agent/build.rs

@@ -13,7 +13,9 @@ fn main() -> Result<()> {
     println!("cargo:rerun-if-changed=../.git/index");
 
     // Build timestamp (UTC)
-    let build_timestamp = chrono::Utc::now().format("%Y-%m-%d %H:%M:%S UTC").to_string();
+    let build_timestamp = chrono::Utc::now()
+        .format("%Y-%m-%d %H:%M:%S UTC")
+        .to_string();
     println!("cargo:rustc-env=BUILD_TIMESTAMP={}", build_timestamp);
 
     // Git commit hash (short)
@@ -53,7 +55,10 @@ fn main() -> Result<()> {
         .ok()
         .map(|o| !o.stdout.is_empty())
         .unwrap_or(false);
-    println!("cargo:rustc-env=GIT_DIRTY={}", if git_dirty { "dirty" } else { "clean" });
+    println!(
+        "cargo:rustc-env=GIT_DIRTY={}",
+        if git_dirty { "dirty" } else { "clean" }
+    );
 
     // Git commit date
     let git_commit_date = Command::new("git")