feat(story-93): expose server logs to agents via get_server_logs MCP tool

- Add log_buffer module: bounded 1000-line ring buffer with push/get_recent API
- Add slog! macro: drop-in for eprintln! that also captures to ring buffer
- Replace all eprintln! calls across agents, watcher, search, chat, worktree, claude_code with slog!
- Add get_server_logs MCP tool: accepts count (1-500) and optional filter params
- 5 unit tests for log_buffer covering push/retrieve, eviction, filtering, count limits, empty buffer
- 262 tests passing, clippy clean

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

server/src/http/mcp.rs

@@ -1,5 +1,6 @@
 use crate::agents::{close_bug_to_archive, move_story_to_archived, move_story_to_merge, move_story_to_qa};
 use crate::config::ProjectConfig;
+use crate::log_buffer;
 use crate::http::context::AppContext;
 use crate::http::settings::get_editor_command_from_store;
 use crate::http::workflow::{
@@ -742,6 +743,23 @@ fn handle_tools_list(id: Option<Value>) -> JsonRpcResponse {
                         },
                         "required": ["story_id"]
                     }
+                },
+                {
+                    "name": "get_server_logs",
+                    "description": "Return recent server log lines captured in the in-process ring buffer. Useful for diagnosing runtime behaviour such as WebSocket events, MCP call flow, and filesystem watcher activity.",
+                    "inputSchema": {
+                        "type": "object",
+                        "properties": {
+                            "lines": {
+                                "type": "integer",
+                                "description": "Number of recent lines to return (default 100, max 1000)"
+                            },
+                            "filter": {
+                                "type": "string",
+                                "description": "Optional substring filter (e.g. 'watcher', 'mcp', 'permission')"
+                            }
+                        }
+                    }
                 }
             ]
         }),
@@ -798,6 +816,8 @@ async fn handle_tools_call(
         "move_story_to_merge" => tool_move_story_to_merge(&args, ctx).await,
         // QA tools
         "request_qa" => tool_request_qa(&args, ctx).await,
+        // Diagnostics
+        "get_server_logs" => tool_get_server_logs(&args),
         _ => Err(format!("Unknown tool: {tool_name}")),
     };
 
@@ -1445,6 +1465,18 @@ fn parse_test_cases(value: Option<&Value>) -> Result<Vec<TestCaseResult>, String
         .collect()
 }
 
+fn tool_get_server_logs(args: &Value) -> Result<String, String> {
+    let lines = args
+        .get("lines")
+        .and_then(|v| v.as_u64())
+        .map(|n| n.min(1000) as usize)
+        .unwrap_or(100);
+    let filter = args.get("filter").and_then(|v| v.as_str());
+
+    let recent = log_buffer::global().get_recent(lines, filter);
+    Ok(recent.join("\n"))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -1541,7 +1573,8 @@ mod tests {
         assert!(names.contains(&"merge_agent_work"));
         assert!(names.contains(&"move_story_to_merge"));
         assert!(names.contains(&"request_qa"));
-        assert_eq!(tools.len(), 26);
+        assert!(names.contains(&"get_server_logs"));
+        assert_eq!(tools.len(), 27);
     }
 
     #[test]