fix(io-core,signer): replace unwrap() with proper error handling (#3150)

* fix(io-core,signer): replace unwrap() with proper error handling

## io-core (issue #653 item 1)
- pool.rs: replace 8 .lock().unwrap() with poisoned recovery
- pool.rs: replace semaphore acquire unwrap with graceful fallback
- deadlock_detector.rs: replace 5 .lock().unwrap() with match/ok

## signer (issue #653 item 1)
- Add SignV2Error enum, try_pre_sign_v2, try_sign_v2
- Replace 14 unwrap() in v2 signing with ? propagation
- Add try_streaming_sign_v4, replace 5 expect("err") with descriptive errors
- get_host_addr returns Result instead of panicking

All backward-compat wrappers preserved. 95 io-core + 18 signer tests pass.

* fix: address signer and pool review comments

* test: update signer v2 string-to-sign test

* fix: address signer and pool review followups

* fix: tighten signer host and pool fallback

crates/io-core/src/deadlock_detector.rs

@@ -155,7 +155,7 @@ impl DeadlockDetector {
     /// Register a new lock.
     pub fn register_lock(&self, lock_type: LockType) -> u64 {
         let id = {
-            let mut next = self.next_lock_id.lock().unwrap();
+            let mut next = self.next_lock_id.lock().unwrap_or_else(|e| e.into_inner());
             *next += 1;
             *next
         };
@@ -243,7 +243,10 @@ impl DeadlockDetector {
             return None;
         }
 
-        let graph = self.wait_graph.lock().unwrap();
+        let graph = match self.wait_graph.lock() {
+            Ok(g) => g,
+            Err(_) => return None,
+        };
 
         // Build adjacency list
         let mut adj: HashMap<u64, Vec<u64>> = HashMap::new();
@@ -310,7 +313,10 @@ impl DeadlockDetector {
             return Vec::new();
         }
 
-        let locks = self.locks.lock().unwrap();
+        let locks = match self.locks.lock() {
+            Ok(l) => l,
+            Err(_) => return Vec::new(),
+        };
         let mut result = Vec::new();
 
         for (&id, info) in locks.iter() {
@@ -349,13 +355,13 @@ impl DeadlockDetector {
 
     /// Get lock info.
     pub fn get_lock_info(&self, lock_id: u64) -> Option<LockInfo> {
-        let locks = self.locks.lock().unwrap();
+        let locks = self.locks.lock().ok()?;
         locks.get(&lock_id).cloned()
     }
 
     /// Get total number of registered locks.
     pub fn lock_count(&self) -> usize {
-        let locks = self.locks.lock().unwrap();
+        let locks = self.locks.lock().unwrap_or_else(|e| e.into_inner());
         locks.len()
     }
 }