fix: resolve logic errors in ahm heal module (#788)

* fix: resolve logic errors in ahm heal module

- Fix response publishing logic in HealChannelProcessor to properly handle errors
- Fix negative index handling in DiskStatusChange event to fail fast instead of silently converting to 0
- Enhance timeout control in heal_erasure_set Step 3 loop to immediately respond to cancellation/timeout
- Add proper error propagation for task cancellation and timeout in bucket healing loop

* fix: stabilize performance impact measurement test

- Increase measurement count from 3 to 5 runs for better stability
- Increase workload from 5000 to 10000 operations for more accurate timing
- Use median of 5 measurements instead of single measurement
- Ensure with_scanner duration is at least baseline to avoid negative overhead
- Increase wait time for scanner state stabilization

* wip

* Update crates/ahm/src/heal/channel.rs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* refactor: remove redundant ok_or_else + expect in event.rs

Replace redundant ok_or_else() + expect() pattern with
unwrap_or_else() + panic!() to avoid creating unnecessary Error
type when the value will panic anyway. This also defers error
message formatting until the error actually occurs.

* Update crates/ahm/src/heal/task.rs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(ahm): fix logic errors and add unit tests

- Fix panic in HealEvent::to_heal_request for invalid indices
- Replace unwrap() calls with proper error handling in resume.rs
- Fix race conditions and timeout calculation in task.rs
- Fix semaphore acquisition error handling in erasure_healer.rs
- Improve error message for large objects in storage.rs
- Add comprehensive unit tests for progress, event, and channel modules
- Fix clippy warning: move test module to end of file in heal_channel.rs

* style: apply cargo fmt formatting

* refactor(ahm): address copilot review suggestions

- Add comment to check_control_flags explaining why return value is discarded
- Fix hardcoded median index in performance test using constant and dynamic calculation

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

crates/common/src/heal_channel.rs

@@ -18,7 +18,7 @@ use std::{
     fmt::{self, Display},
     sync::OnceLock,
 };
-use tokio::sync::mpsc;
+use tokio::sync::{broadcast, mpsc};
 use uuid::Uuid;
 
 pub const HEAL_DELETE_DANGLING: bool = true;
@@ -192,6 +192,11 @@ pub type HealChannelReceiver = mpsc::UnboundedReceiver<HealChannelCommand>;
 /// Global heal channel sender
 static GLOBAL_HEAL_CHANNEL_SENDER: OnceLock<HealChannelSender> = OnceLock::new();
 
+type HealResponseSender = broadcast::Sender<HealChannelResponse>;
+
+/// Global heal response broadcaster
+static GLOBAL_HEAL_RESPONSE_SENDER: OnceLock<HealResponseSender> = OnceLock::new();
+
 /// Initialize global heal channel
 pub fn init_heal_channel() -> HealChannelReceiver {
     let (tx, rx) = mpsc::unbounded_channel();
@@ -218,6 +223,23 @@ pub async fn send_heal_command(command: HealChannelCommand) -> Result<(), String
     }
 }
 
+fn heal_response_sender() -> &'static HealResponseSender {
+    GLOBAL_HEAL_RESPONSE_SENDER.get_or_init(|| {
+        let (tx, _rx) = broadcast::channel(1024);
+        tx
+    })
+}
+
+/// Publish a heal response to subscribers.
+pub fn publish_heal_response(response: HealChannelResponse) -> Result<(), broadcast::error::SendError<HealChannelResponse>> {
+    heal_response_sender().send(response).map(|_| ())
+}
+
+/// Subscribe to heal responses.
+pub fn subscribe_heal_responses() -> broadcast::Receiver<HealChannelResponse> {
+    heal_response_sender().subscribe()
+}
+
 /// Send heal start request
 pub async fn send_heal_request(request: HealChannelRequest) -> Result<(), String> {
     send_heal_command(HealChannelCommand::Start(request)).await
@@ -415,3 +437,20 @@ pub async fn send_heal_disk(set_disk_id: String, priority: Option<HealChannelPri
     };
     send_heal_request(req).await
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn heal_response_broadcast_reaches_subscriber() {
+        let mut receiver = subscribe_heal_responses();
+        let response = create_heal_response("req-1".to_string(), true, None, None);
+
+        publish_heal_response(response.clone()).expect("publish should succeed");
+
+        let received = receiver.recv().await.expect("should receive heal response");
+        assert_eq!(received.request_id, response.request_id);
+        assert!(received.success);
+    }
+}