Move fixed_filter_json from g3-core to g3-cli

Properly separates UI display concern from core library:
- fixed_filter_json module now lives in g3-cli (UI layer)
- UiWriter trait gains filter_json_tool_calls() and reset_json_filter() methods
- g3-core delegates filtering to UI layer via trait methods
- Different UiWriter implementations can choose their own filtering behavior
- ConsoleUiWriter filters JSON tool calls for clean terminal display
- MachineUiWriter/NullUiWriter use default pass-through

Benefits:
- Proper separation of concerns
- Core stays clean without display-specific logic
- Testability - filter can be tested independently in g3-cli

crates/g3-core/src/feedback_extraction.rs

@@ -139,8 +139,16 @@ fn try_extract_from_session_log(
     session_id: &str,
     config: &FeedbackExtractionConfig,
 ) -> Option<String> {
-    let logs_path = config.logs_dir.clone().unwrap_or_else(logs_dir);
-    let log_file_path = logs_path.join(format!("g3_session_{}.json", session_id));
+    // Try new .g3/sessions/<session_id>/session.json path first
+    let log_file_path = crate::get_session_file(session_id);
+    
+    // Fall back to old logs/ path if new path doesn't exist
+    let log_file_path = if log_file_path.exists() {
+        log_file_path
+    } else {
+        let logs_path = config.logs_dir.clone().unwrap_or_else(logs_dir);
+        logs_path.join(format!("g3_session_{}.json", session_id))
+    };
 
     if !log_file_path.exists() {
         debug!("Session log file not found: {:?}", log_file_path);
@@ -275,8 +283,16 @@ fn try_extract_from_conversation_history(
     session_id: &str,
     config: &FeedbackExtractionConfig,
 ) -> Option<String> {
-    let logs_path = config.logs_dir.clone().unwrap_or_else(logs_dir);
-    let log_file_path = logs_path.join(format!("g3_session_{}.json", session_id));
+    // Try new .g3/sessions/<session_id>/session.json path first
+    let log_file_path = crate::get_session_file(session_id);
+    
+    // Fall back to old logs/ path if new path doesn't exist
+    let log_file_path = if log_file_path.exists() {
+        log_file_path
+    } else {
+        let logs_path = config.logs_dir.clone().unwrap_or_else(logs_dir);
+        logs_path.join(format!("g3_session_{}.json", session_id))
+    };
 
     if !log_file_path.exists() {
         return None;