brokerd: escape container errors in the log; prefix and quote two messages

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

crates/brokerd/src/config.rs

@@ -176,7 +176,7 @@ impl Config {
         }
         if let Some(runner) = &config.runner {
             let where_image = format!(
-                "[runner] image is {}; it must be named by digest: <name>@sha256:<64 hex digits>",
+                "[runner] image is {:?}; it must be named by digest: <name>@sha256:<64 hex digits>",
                 runner.image
             );
             let (name, hex) = match runner.image.rsplit_once("@sha256:") {
@@ -198,7 +198,7 @@ impl Config {
                 return Err(ConfigError::Invalid(
                     path.to_path_buf(),
                     format!(
-                        "[runner] memory is {}; it must be a number and one of b, k, m, g",
+                        "[runner] memory is {:?}; it must be a number and one of b, k, m, g",
                         runner.memory
                     ),
                 ));

crates/brokerd/src/container.rs

@@ -214,16 +214,20 @@ impl Podman {
                     truncated,
                 }),
                 Some(2) => {
-                    (self.log)(err);
+                    (self.log)(&format!("brokerd: {name}: the tool could not run: {err:?}"));
                     Err(RunError::Failed(COULD_NOT_RUN.to_string()))
                 }
                 Some(125..=127) => {
-                    (self.log)(&format!("{err}\n{RUNBOOK}"));
+                    (self.log)(&format!(
+                        "brokerd: podman could not start {name}: {err:?}\n{RUNBOOK}"
+                    ));
                     Err(RunError::Unavailable(CANNOT_START.to_string()))
                 }
                 Some(137) => Err(RunError::Failed(KILLED.to_string())),
                 _ => {
-                    (self.log)(&format!("brokerd: container {name} exited {status}\n{err}"));
+                    (self.log)(&format!(
+                        "brokerd: container {name} exited {status}: {err:?}"
+                    ));
                     Err(RunError::Failed(UNEXPECTED.to_string()))
                 }
             },
@@ -302,7 +306,7 @@ impl Podman {
             Ok(output) => {
                 let stderr = String::from_utf8_lossy(&output.stderr).into_owned();
                 (self.log)(&format!(
-                    "brokerd: podman could not start {name}-egress: {stderr}\n{RUNBOOK}"
+                    "brokerd: podman could not start {name}-egress: {stderr:?}\n{RUNBOOK}"
                 ));
                 return Err(RunError::Unavailable(CANNOT_START.to_string()));
             }

crates/brokerd/src/main.rs

@@ -97,7 +97,7 @@ fn main() -> ExitCode {
         broker_path.display(),
         admin_path.display()
     );
-    eprintln!("{runtime_notice}");
+    eprintln!("brokerd: {runtime_notice}");
 
     match started.run() {
         Ok(()) => ExitCode::SUCCESS,