fix(startup): unify agent startup with beacon + instructions in CLI prompt (#977)

All agents now receive their startup beacon + role-specific instructions via
the CLI prompt, making sessions identifiable in /resume picker while removing
unreliable post-startup nudges.

Changes:
- Rename FormatStartupNudge → FormatStartupBeacon, StartupNudgeConfig → BeaconConfig
- Remove StartupNudge() function (no longer needed)
- Remove PropulsionNudge() and PropulsionNudgeForRole() functions
- Update deacon, witness, refinery, polecat managers to include beacon in CLI prompt
- Update boot to inline beacon (can't import session due to import cycle)
- Update daemon/lifecycle.go to include beacon via BuildCommandWithPrompt
- Update cmd/deacon.go to include beacon in startup command
- Remove redundant StartupNudge and PropulsionNudge calls from all startup paths

The beacon is now part of the CLI prompt which is queued before Claude starts,
making it more reliable than post-startup nudges which had timing issues.
SessionStart hook runs gt prime automatically, so PropulsionNudge was redundant.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

internal/session/startup_test.go

@@ -5,16 +5,16 @@ import (
 	"testing"
 )
 
-func TestFormatStartupNudge(t *testing.T) {
+func TestFormatStartupBeacon(t *testing.T) {
 	tests := []struct {
 		name     string
-		cfg      StartupNudgeConfig
+		cfg      BeaconConfig
 		wantSub  []string // substrings that must appear
 		wantNot  []string // substrings that must NOT appear
 	}{
 		{
 			name: "assigned with mol-id",
-			cfg: StartupNudgeConfig{
+			cfg: BeaconConfig{
 				Recipient: "gastown/crew/gus",
 				Sender:    "deacon",
 				Topic:     "assigned",
@@ -31,7 +31,7 @@ func TestFormatStartupNudge(t *testing.T) {
 		},
 		{
 			name: "cold-start no mol-id",
-			cfg: StartupNudgeConfig{
+			cfg: BeaconConfig{
 				Recipient: "deacon",
 				Sender:    "mayor",
 				Topic:     "cold-start",
@@ -49,7 +49,7 @@ func TestFormatStartupNudge(t *testing.T) {
 		},
 		{
 			name: "handoff self",
-			cfg: StartupNudgeConfig{
+			cfg: BeaconConfig{
 				Recipient: "gastown/witness",
 				Sender:    "self",
 				Topic:     "handoff",
@@ -66,7 +66,7 @@ func TestFormatStartupNudge(t *testing.T) {
 		},
 		{
 			name: "mol-id only",
-			cfg: StartupNudgeConfig{
+			cfg: BeaconConfig{
 				Recipient: "gastown/polecats/Toast",
 				Sender:    "witness",
 				MolID:     "gt-xyz99",
@@ -80,7 +80,7 @@ func TestFormatStartupNudge(t *testing.T) {
 		},
 		{
 			name: "empty topic defaults to ready",
-			cfg: StartupNudgeConfig{
+			cfg: BeaconConfig{
 				Recipient: "deacon",
 				Sender:    "mayor",
 			},
@@ -91,7 +91,7 @@ func TestFormatStartupNudge(t *testing.T) {
 		},
 		{
 			name: "start includes fallback instructions",
-			cfg: StartupNudgeConfig{
+			cfg: BeaconConfig{
 				Recipient: "beads/crew/fang",
 				Sender:    "human",
 				Topic:     "start",
@@ -106,7 +106,7 @@ func TestFormatStartupNudge(t *testing.T) {
 		},
 		{
 			name: "restart includes fallback instructions",
-			cfg: StartupNudgeConfig{
+			cfg: BeaconConfig{
 				Recipient: "gastown/crew/george",
 				Sender:    "human",
 				Topic:     "restart",
@@ -122,19 +122,55 @@ func TestFormatStartupNudge(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got := FormatStartupNudge(tt.cfg)
+			got := FormatStartupBeacon(tt.cfg)
 
 			for _, sub := range tt.wantSub {
 				if !strings.Contains(got, sub) {
-					t.Errorf("FormatStartupNudge() = %q, want to contain %q", got, sub)
+					t.Errorf("FormatStartupBeacon() = %q, want to contain %q", got, sub)
 				}
 			}
 
 			for _, sub := range tt.wantNot {
 				if strings.Contains(got, sub) {
-					t.Errorf("FormatStartupNudge() = %q, should NOT contain %q", got, sub)
+					t.Errorf("FormatStartupBeacon() = %q, should NOT contain %q", got, sub)
 				}
 			}
 		})
 	}
 }
+
+func TestBuildStartupPrompt(t *testing.T) {
+	// BuildStartupPrompt combines beacon + instructions
+	cfg := BeaconConfig{
+		Recipient: "deacon",
+		Sender:    "daemon",
+		Topic:     "patrol",
+	}
+	instructions := "Start patrol immediately."
+
+	got := BuildStartupPrompt(cfg, instructions)
+
+	// Should contain beacon parts
+	if !strings.Contains(got, "[GAS TOWN]") {
+		t.Errorf("BuildStartupPrompt() missing beacon header")
+	}
+	if !strings.Contains(got, "deacon") {
+		t.Errorf("BuildStartupPrompt() missing recipient")
+	}
+	if !strings.Contains(got, "<- daemon") {
+		t.Errorf("BuildStartupPrompt() missing sender")
+	}
+	if !strings.Contains(got, "patrol") {
+		t.Errorf("BuildStartupPrompt() missing topic")
+	}
+
+	// Should contain instructions after beacon
+	if !strings.Contains(got, instructions) {
+		t.Errorf("BuildStartupPrompt() missing instructions")
+	}
+
+	// Should have blank line between beacon and instructions
+	if !strings.Contains(got, "\n\n"+instructions) {
+		t.Errorf("BuildStartupPrompt() missing blank line before instructions")
+	}
+}