Quiet only the stdout UI under --json, not the log level (closes #112)

Per the decision on the issue (option 1), --json no longer implies Quiet. Folding --json into Quiet pinned the stderr log level to WARN, so prune --json gave a machine consumer no record of the local index rows it deleted. The two effects are now split: a JSON field on log.Options drives only the stdout UI-quiet in setupGlobals, keeping the JSON document clean, while the stderr log level follows --verbose/--debug again (diagnostics have gone to stderr since #82). The same coupling is removed for snapshot verify, snapshot remove and remote info; snapshot list was already decoupled.

Model: opus-4-8

internal/log/module.go

@@ -14,8 +14,18 @@ var Module = fx.Module("log",
 )
 
 // New creates a new logger configuration from provided options.
+//
+// JSON is intentionally not carried into Config: a command emitting a
+// JSON document on stdout must keep its stderr log level under
+// --verbose/--debug, so --json must not lower it (issue #112). JSON
+// silences the stdout UI in setupGlobals instead.
 func New(opts Options) Config {
-	return Config(opts)
+	return Config{
+		Verbose: opts.Verbose,
+		Debug:   opts.Debug,
+		Cron:    opts.Cron,
+		Quiet:   opts.Quiet,
+	}
 }
 
 // Options are provided by the CLI.
@@ -24,4 +34,8 @@ type Options struct {
 	Debug   bool
 	Cron    bool
 	Quiet   bool
+	// JSON marks a command whose stdout carries a machine-readable
+	// document. It silences the human UI on stdout (see setupGlobals),
+	// but unlike Quiet it leaves the stderr log level alone.
+	JSON bool
 }