Migrate logging to go-mana-component; delete logging/ package

Replaces the flat key-value logging scheme with component-based structured
logging via go-mana-component. Each layer (pool, worker, connection) builds
its own component identity and derives a *slog.Logger from a caller-supplied
slog.Handler.

- Delete logging/ package (logging.go, logging_test.go)
- Strip LoggingEnabled and LogLevel from ConnectionConfig, PoolConfig,
 WorkerConfig; remove associated option funcs
- Change NewConnection and NewConnectionFromSocket to accept ctx and
 slog.Handler instead of *slog.Logger; constructors build component
 identity via MustNew/MustExtend internally
- Change WorkerFactory, NewWorker, connect, and RunDialer to carry
 slog.Handler; remove PoolPlugin.Handler
- Change NewPool to establish pool component identity via MustNew;
 remove pool_id field, PoolPlugin.ID, and ErrInvalidPoolID
- Fix data race in MockSlogHandler: WithAttrs now shares parent mutex
 pointer rather than allocating a new one per child
- Run go fix

transport/config.go

@@ -1,7 +1,6 @@
 package transport
 
 import (
-	"log/slog"
 	"net/http"
 	"time"
 )
@@ -15,8 +14,6 @@ type ConnectionConfig struct {
 	PingInterval       time.Duration
 	IncomingBufferSize int
 	ErrorsBufferSize   int
-	LoggingEnabled     bool
-	LogLevel           *slog.Level
 	Retry              *RetryConfig
 }
 
@@ -50,8 +47,6 @@ func GetDefaultConnectionConfig() *ConnectionConfig {
 		PingInterval:       20 * time.Second,
 		IncomingBufferSize: 100,
 		ErrorsBufferSize:   10,
-		LoggingEnabled:     true,
-		LogLevel:           nil,
 		Retry:              GetDefaultRetryConfig(),
 	}
 }
@@ -216,21 +211,6 @@ func WithErrorsBufferSize(value int) ConnectionOption {
 	}
 }
 
-func WithLoggingEnabled(value bool) ConnectionOption {
-	return func(c *ConnectionConfig) error {
-		c.LoggingEnabled = value
-		return nil
-	}
-}
-
-func WithLogLevel(level slog.Level) ConnectionOption {
-	return func(c *ConnectionConfig) error {
-		l := level
-		c.LogLevel = &l
-		return nil
-	}
-}
-
 func WithoutRetry() ConnectionOption {
 	return func(c *ConnectionConfig) error {
 		c.Retry = nil