fix(serve-mcp): TelemetryRecorder migration, McpToolCallLogger, stdio tracing

[deer]

• JUL → TelemetryRecorder. McpServer drops java.util.logging entirely and routes all server-level output through a TelemetryRecorder injected via Builder.recorder(...).

• Stdout pollution fix. The default recorder previously split output between System.out (info/diagnostic) and System.err (warn/error). In stdio mode System.out is the NDJSON protocol channel, so info and diagnostic output silently corrupted the stream. The default is now PrintStreamTelemetryRecorder.of(..., System.err, System.err). A new test reproduces the bug by redirecting System.out before building the server and asserting that every byte on the protocol stream is valid JSON.

• Request/response tracing. dispatch() records a diagnostic before and after every handled method, giving stdio and HTTP callers a trace of what the server saw and responded to.

• Clean EOF vs broken pipe. stdioLoop previously swallowed all IOExceptions silently. It now records an info event on clean EOF and a warn event (with the exception message) on any unexpected IOException.

• McpToolCallLogger. New Subscriber<ToolCallEvent> that logs STARTED at diagnostic level, SUCCEEDED at info (or warn when the call exceeds the slow-call threshold, default 5 s), and FAILED at warn with the thrown exception. Attach manually via mcpServer.toolCallEvents().subscribe(McpToolCallLogger.of(recorder)) or enable at build time via Builder.logToolCalls(), which wires the logger to the server's own recorder automatically.