fix(storage): harden offline drive fail-fast paths (#2564)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

crates/heal/src/error.rs

@@ -68,6 +68,9 @@ pub enum Error {
     #[error("Invalid heal type: {heal_type}")]
     InvalidHealType { heal_type: String },
 
+    #[error("Transient heal skip: {message}")]
+    TransientSkip { message: String },
+
     #[error("Heal task cancelled")]
     TaskCancelled,
 
@@ -92,6 +95,11 @@ impl Error {
     {
         Error::Other(error.into().to_string())
     }
+
+    /// Create a transient skip error for retryable background heal checks.
+    pub fn transient_skip(message: impl Into<String>) -> Self {
+        Error::TransientSkip { message: message.into() }
+    }
 }
 
 impl From<Error> for std::io::Error {