feat(memory): add session_id isolation to Memory trait (#530)

* feat(memory): add session_id isolation to Memory trait

Add optional session_id parameter to store(), recall(), and list()
methods across the Memory trait and all four backends (sqlite, markdown,
lucid, none). This enables per-session memory isolation so different
agent sessions cannot cross-read each other's stored memories.

Changes:
- traits.rs: Add session_id: Option<&str> to store/recall/list
- sqlite.rs: Schema migration (ALTER TABLE ADD COLUMN session_id),
  index, persist/filter by session_id in all query paths
- markdown.rs, lucid.rs, none.rs: Updated signatures
- All callers pass None for backward compatibility
- 5 new tests: session-filtered recall, cross-session isolation,
  session-filtered list, no-filter returns all, migration idempotency

Closes #518

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

* fix(channels): fix discord _channel_id typo and lark missing reply_to

Pre-existing compilation errors on main after reply_to was added to
ChannelMessage: discord.rs used _channel_id (underscore prefix) but
referenced channel_id, and lark.rs was missing the reply_to field.

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/memory/none.rs

@@ -25,11 +25,17 @@ impl Memory for NoneMemory {
         _key: &str,
         _content: &str,
         _category: MemoryCategory,
+        _session_id: Option<&str>,
     ) -> anyhow::Result<()> {
         Ok(())
     }
 
-    async fn recall(&self, _query: &str, _limit: usize) -> anyhow::Result<Vec<MemoryEntry>> {
+    async fn recall(
+        &self,
+        _query: &str,
+        _limit: usize,
+        _session_id: Option<&str>,
+    ) -> anyhow::Result<Vec<MemoryEntry>> {
         Ok(Vec::new())
     }
 
@@ -37,7 +43,11 @@ impl Memory for NoneMemory {
         Ok(None)
     }
 
-    async fn list(&self, _category: Option<&MemoryCategory>) -> anyhow::Result<Vec<MemoryEntry>> {
+    async fn list(
+        &self,
+        _category: Option<&MemoryCategory>,
+        _session_id: Option<&str>,
+    ) -> anyhow::Result<Vec<MemoryEntry>> {
         Ok(Vec::new())
     }
 
@@ -62,11 +72,14 @@ mod tests {
     async fn none_memory_is_noop() {
         let memory = NoneMemory::new();
 
-        memory.store("k", "v", MemoryCategory::Core).await.unwrap();
+        memory
+            .store("k", "v", MemoryCategory::Core, None)
+            .await
+            .unwrap();
 
         assert!(memory.get("k").await.unwrap().is_none());
-        assert!(memory.recall("k", 10).await.unwrap().is_empty());
-        assert!(memory.list(None).await.unwrap().is_empty());
+        assert!(memory.recall("k", 10, None).await.unwrap().is_empty());
+        assert!(memory.list(None, None).await.unwrap().is_empty());
         assert!(!memory.forget("k").await.unwrap());
         assert_eq!(memory.count().await.unwrap(), 0);
         assert!(memory.health_check().await);