Fix daemon socket ready race condition (bd-151)

Add WaitReady() channel to RPC server that signals when the socket is
listening and ready to accept connections. Previously daemon startup
waited a fixed 2 seconds which could fail if the server took longer.

Changes:
- Add readyChan to Server struct
- Signal ready after listener bind completes
- Update daemon startup to wait on WaitReady() channel
- Increase timeout to 5s with proper signaling

This fixes multi-repo daemon routing test failures where daemon would
start but not be ready to handle requests within the timeout window.

Amp-Thread-ID: https://ampcode.com/threads/T-675a2db5-b1b3-480d-a108-b003d8139d08
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/server.go

@@ -60,6 +60,8 @@ type Server struct {
 	connSemaphore chan struct{}
 	// Request timeout
 	requestTimeout time.Duration
+	// Ready channel signals when server is listening
+	readyChan      chan struct{}
 }
 
 // NewServer creates a new RPC server
@@ -108,6 +110,7 @@ func NewServer(socketPath string, store storage.Storage) *Server {
 		maxConns:       maxConns,
 		connSemaphore:  make(chan struct{}, maxConns),
 		requestTimeout: requestTimeout,
+		readyChan:      make(chan struct{}),
 	}
 }
 
@@ -137,6 +140,9 @@ func (s *Server) Start(ctx context.Context) error {
 	s.listener = listener
 	s.mu.Unlock()
 
+	// Signal that server is ready to accept connections
+	close(s.readyChan)
+
 	go s.handleSignals()
 	go s.runCleanupLoop()
 
@@ -177,6 +183,11 @@ func (s *Server) Start(ctx context.Context) error {
 	}
 }
 
+// WaitReady waits for the server to be ready to accept connections
+func (s *Server) WaitReady() <-chan struct{} {
+	return s.readyChan
+}
+
 // Stop stops the RPC server and cleans up resources
 func (s *Server) Stop() error {
 	var err error