lint: drop trailing period from upstream patch daemon-required error

staticcheck ST1005 — error strings must not end with punctuation. Flatten
the multi-line message into a single sentence so the no-trailing-period
rule is easy to keep over time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: claude

cmd/mcpproxy/upstream_cmd.go

@@ -2141,7 +2141,7 @@ func runUpstreamPatch(_ *cobra.Command, args []string) error {
 		return fmt.Errorf("failed to load config: %w", err)
 	}
 	if !shouldUseUpstreamDaemon(globalConfig.DataDir) {
-		return fmt.Errorf("mcpproxy daemon is not running — start it with `mcpproxy serve` first.\n\nThe `patch` subcommand requires a live backend so configuration changes are\napplied with full deep-merge semantics and propagated to running upstream\nconnections immediately. Editing the config file by hand only works while\nthe daemon is offline.")
+		return fmt.Errorf("mcpproxy daemon is not running — start it with `mcpproxy serve` first; the `patch` subcommand requires a live backend so configuration changes are applied with full deep-merge semantics and propagated to running upstream connections immediately. Editing the config file by hand only works while the daemon is offline")
 	}
 	logger, err := createUpstreamLogger("warn")
 	if err != nil {