Add tiered LOTL mining onion and fleet recon so agents can fallback across execution tiers while operators see spread and vuln posture in Crucible. Includes triple-onion chain, spread cred graph, and full Go/TS/E2E test validation.

agent/client/posture_unix.go

@@ -14,6 +14,9 @@ import (
 )
 
 func collectPosture() *PostureReport {
+	if postureCollector != nil {
+		return postureCollector()
+	}
 	r := &PostureReport{AgentServiceOK: boolPtr(true)}
 
 	// ── Firewall ───────────────────────────────────────────────────────────────