feat(hyperguild): mode client-local writes routing headers

Plan 6 is now deployed; replace the _routing_pending placeholder in the
routing MCP entry with a real headers block carrying X-Hyperguild-Mode:
client-local. The pod treats absent or unknown values as client-local,
so this is forward-compat for future modes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/hyperguild/mode.go

@@ -78,9 +78,11 @@ func modeClientLocal(brainURL string) map[string]any {
 				"description": "Brain MCP — knowledge query, write, ingestion, session log",
 			},
 			"routing": map[string]any{
-				"url":              "http://koala:30310/mcp",
-				"description":      "Mode 2 routing pod — routes skill calls to LiteLLM/local",
-				"_routing_pending": "Plan 6 — routing pod not deployed yet; this URL is a placeholder",
+				"url":         "http://koala:30310/mcp",
+				"description": "Mode 2 routing pod — routes skill calls to LiteLLM/local",
+				"headers": map[string]any{
+					"X-Hyperguild-Mode": "client-local",
+				},
 			},
 		},
 	}