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

--json was folded into Quiet, which pinned the stderr log level to WARN.
So `prune --json` gave a machine consumer no record of the local index
rows it deleted, even under --verbose: the audit records were gated off
stdout and pinned below the level on stderr.

--json now quiets only the stdout UI, keeping the JSON document clean
(issue #108); the stderr log level follows --verbose/--debug again, since
diagnostics have gone to stderr since #82. The same coupling is removed
for `snapshot verify`, `snapshot remove`, and `remote info`, which
carried it for the same outdated reason.

A test asserts `--verbose prune --json` emits the cleanup record on
stderr while stdout stays exactly one document, and that --json alone
keeps it below the level.

model: claude-opus-4-8

internal/cli/snapshot.go

@@ -239,7 +239,8 @@ func newSnapshotVerifyCommand() *cobra.Command {
 				LogOptions: log.Options{
 					Verbose: rootFlags.Verbose,
 					Debug:   rootFlags.Debug,
-					Quiet:   rootFlags.Quiet || opts.JSON,
+					Quiet:   rootFlags.Quiet,
+					JSON:    opts.JSON,
 				},
 				Modules: []fx.Option{},
 				Invokes: []fx.Option{