fix(discord): use channel_id instead of sender for replies (fixes #483)

fix(misc): complete parking_lot::Mutex migration (fixes #505)

- DiscordChannel: store actual channel_id in ChannelMessage.channel
  instead of hardcoded "discord" string
- channels/mod.rs: use msg.channel instead of msg.sender for replies
- Migrate all std::sync::Mutex to parking_lot::Mutex:
  * src/security/audit.rs
  * src/memory/sqlite.rs
  * src/memory/response_cache.rs
  * src/memory/lucid.rs
  * src/channels/email_channel.rs
  * src/gateway/mod.rs
  * src/observability/traits.rs
  * src/providers/reliable.rs
  * src/providers/router.rs
  * src/agent/agent.rs
- Remove all .lock().unwrap() and .map_err(PoisonError) patterns
  since parking_lot::Mutex never poisons

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/memory/response_cache.rs

@@ -10,7 +10,7 @@ use chrono::{Duration, Local};
 use rusqlite::{params, Connection};
 use sha2::{Digest, Sha256};
 use std::path::{Path, PathBuf};
-use std::sync::Mutex;
+use parking_lot::Mutex;
 
 /// Response cache backed by a dedicated SQLite database.
 ///
@@ -77,10 +77,7 @@ impl ResponseCache {
 
     /// Look up a cached response. Returns `None` on miss or expired entry.
     pub fn get(&self, key: &str) -> Result<Option<String>> {
-        let conn = self
-            .conn
-            .lock()
-            .map_err(|e| anyhow::anyhow!("Lock error: {e}"))?;
+        let conn = self.conn.lock();
 
         let now = Local::now();
         let cutoff = (now - Duration::minutes(self.ttl_minutes)).to_rfc3339();
@@ -108,10 +105,7 @@ impl ResponseCache {
 
     /// Store a response in the cache.
     pub fn put(&self, key: &str, model: &str, response: &str, token_count: u32) -> Result<()> {
-        let conn = self
-            .conn
-            .lock()
-            .map_err(|e| anyhow::anyhow!("Lock error: {e}"))?;
+        let conn = self.conn.lock();
 
         let now = Local::now().to_rfc3339();
 
@@ -146,10 +140,7 @@ impl ResponseCache {
 
     /// Return cache statistics: (total_entries, total_hits, total_tokens_saved).
     pub fn stats(&self) -> Result<(usize, u64, u64)> {
-        let conn = self
-            .conn
-            .lock()
-            .map_err(|e| anyhow::anyhow!("Lock error: {e}"))?;
+        let conn = self.conn.lock();
 
         let count: i64 =
             conn.query_row("SELECT COUNT(*) FROM response_cache", [], |row| row.get(0))?;
@@ -172,10 +163,7 @@ impl ResponseCache {
 
     /// Wipe the entire cache (useful for `zeroclaw cache clear`).
     pub fn clear(&self) -> Result<usize> {
-        let conn = self
-            .conn
-            .lock()
-            .map_err(|e| anyhow::anyhow!("Lock error: {e}"))?;
+        let conn = self.conn.lock();
 
         let affected = conn.execute("DELETE FROM response_cache", [])?;
         Ok(affected)