feat: add slog structured logging

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pkg/config/config.go

@@ -14,6 +14,7 @@ type Config struct {
 	Server    ServerConfig    `yaml:"server"`
 	Workspace WorkspaceConfig `yaml:"workspace"`
 	Process   ProcessConfig   `yaml:"process"`
+	Log       LogConfig       `yaml:"log"`
 }
 
 // ServerConfig holds HTTP server settings.
@@ -35,12 +36,19 @@ type ProcessConfig struct {
 	OpenCodeCommand string `yaml:"opencodeCommand"`
 }
 
+// LogConfig holds structured logging settings.
+type LogConfig struct {
+	Level  string `yaml:"level"`
+	Format string `yaml:"format"`
+}
+
 // rawConfig is used for YAML deserialization so that duration strings can be
 // parsed explicitly rather than relying on implicit time.Duration unmarshalling.
 type rawConfig struct {
 	Server    rawServerConfig `yaml:"server"`
 	Workspace WorkspaceConfig `yaml:"workspace"`
 	Process   ProcessConfig   `yaml:"process"`
+	Log       LogConfig       `yaml:"log"`
 }
 
 type rawServerConfig struct {
@@ -63,6 +71,7 @@ func Default() Config {
 		},
 		Workspace: WorkspaceConfig{Root: "./workspaces"},
 		Process:   ProcessConfig{OpenCodeCommand: "opencode"},
+		Log:       LogConfig{Level: "info", Format: "json"},
 	}
 }
 
@@ -112,6 +121,12 @@ func applyRaw(cfg *Config, raw rawConfig) error {
 	if raw.Process.OpenCodeCommand != "" {
 		cfg.Process.OpenCodeCommand = raw.Process.OpenCodeCommand
 	}
+	if raw.Log.Level != "" {
+		cfg.Log.Level = raw.Log.Level
+	}
+	if raw.Log.Format != "" {
+		cfg.Log.Format = raw.Log.Format
+	}
 	return nil
 }
 
@@ -159,5 +174,11 @@ func applyEnv(cfg *Config) error {
 	if v := os.Getenv("CODESPACE_OPENCODE_COMMAND"); v != "" {
 		cfg.Process.OpenCodeCommand = v
 	}
+	if v := os.Getenv("CODESPACE_LOG_LEVEL"); v != "" {
+		cfg.Log.Level = v
+	}
+	if v := os.Getenv("CODESPACE_LOG_FORMAT"); v != "" {
+		cfg.Log.Format = v
+	}
 	return nil
 }