fix(server): embed git SHA and build date in server binary

The server used option_env!() for FABRO_GIT_SHA and FABRO_BUILD_DATE,
but no build.rs set them — so `fabro version` always showed "unknown".
Add a build.rs to fabro-server (matching fabro-cli's) and remove the
Sandbox line from `fabro system info`.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/crates/fabro-cli/src/commands/system/info.rs

@@ -66,10 +66,6 @@ pub(super) async fn info_command(
                 .and_then(|runs| runs.active)
                 .unwrap_or_default()
         );
-        println!(
-            "Sandbox: {}",
-            response.sandbox_provider.as_deref().unwrap_or("unknown")
-        );
         println!("Uptime: {}s", response.uptime_secs.unwrap_or_default());
     }
 

lib/crates/fabro-server/Cargo.toml

@@ -79,6 +79,9 @@ walkdir.workspace = true
 multer = "3"
 thiserror.workspace = true
 
+[build-dependencies]
+chrono = { workspace = true }
+
 [dev-dependencies]
 tokio = { workspace = true, features = ["test-util", "macros"] }
 tower = "0.5"

lib/crates/fabro-server/build.rs

@@ -0,0 +1,27 @@
+#[expect(
+    clippy::disallowed_methods,
+    reason = "Build scripts run outside Tokio and need a synchronous git probe for the embedded build SHA."
+)]
+fn main() {
+    println!("cargo:rerun-if-changed=../../../.git/HEAD");
+
+    let sha = std::process::Command::new("git")
+        .args(["rev-list", "-1", "HEAD"])
+        .output()
+        .ok()
+        .and_then(|o| {
+            if o.status.success() {
+                String::from_utf8(o.stdout)
+                    .ok()
+                    .map(|s| s.trim().to_string())
+            } else {
+                None
+            }
+        })
+        .unwrap_or_default();
+    let short_sha = if sha.len() >= 7 { &sha[..7] } else { &sha };
+    println!("cargo:rustc-env=FABRO_GIT_SHA={short_sha}");
+
+    let build_date = chrono::Utc::now().format("%Y-%m-%d").to_string();
+    println!("cargo:rustc-env=FABRO_BUILD_DATE={build_date}");
+}