Logging: structured slog messages throughout, and WithLogger options so callers choose the logger

Log messages are lower-case event names with their details as key/value
attributes ("error" for errors), in place of formatted strings.

Loggable package take a WithLogger option as part of their "New*" call,
defaulting to slog.Default(). Each tags its lines with its `component`.

Some debug loggers print directly rather than using slog when in
terminal logging mode.

internal/cli/migrate/status.go

@@ -75,13 +75,13 @@ func commandStatus(opts *cli.Options) *cobra.Command {
 		Short: "Show which migrations have been applied to the SQLite database",
 		Args:  cobra.NoArgs,
 		PersistentPreRun: func(cmd *cobra.Command, args []string) {
-			slog.Debug("migrate.status.PersistentPreRun")
+			slog.Debug("command persistent pre-run", "command", "migrate.status")
 		},
 		PersistentPostRun: func(cmd *cobra.Command, args []string) {
-			slog.Debug("migrate.status.PersistentPostRun")
+			slog.Debug("command persistent post-run", "command", "migrate.status")
 		},
 		RunE: func(cmd *cobra.Command, args []string) (err error) {
-			slog.Debug("migrate.status.Run")
+			slog.Debug("command run", "command", "migrate.status")
 
 			m, db, err := openMigrator(cmd, opts, false, false)
 			if err != nil {