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/witness/manager.go

@@ -182,20 +182,6 @@ func (m *Manager) Start(foreground bool, agentOverride string, envOverrides []st
 
 	time.Sleep(constants.ShutdownNotifyDelay)
 
-	// Inject startup nudge for predecessor discovery via /resume
-	address := fmt.Sprintf("%s/witness", m.rig.Name)
-	_ = session.StartupNudge(t, sessionID, session.StartupNudgeConfig{
-		Recipient: address,
-		Sender:    "deacon",
-		Topic:     "patrol",
-	}) // Non-fatal
-
-	// GUPP: Gas Town Universal Propulsion Principle
-	// Send the propulsion nudge to trigger autonomous patrol execution.
-	// Wait for beacon to be fully processed (needs to be separate prompt)
-	time.Sleep(2 * time.Second)
-	_ = t.NudgeSession(sessionID, session.PropulsionNudgeForRole("witness", witnessDir)) // Non-fatal
-
 	return nil
 }
 
@@ -236,9 +222,11 @@ func buildWitnessStartCommand(rigPath, rigName, townRoot, agentOverride string,
 	if roleConfig != nil && roleConfig.StartCommand != "" {
 		return beads.ExpandRolePattern(roleConfig.StartCommand, townRoot, rigName, "", "witness"), nil
 	}
-	// Add initial prompt for autonomous patrol startup.
-	// The prompt triggers GUPP: witness starts patrol immediately without waiting for input.
-	initialPrompt := "I am Witness for " + rigName + ". Start patrol: check gt hook, if empty create mol-witness-patrol wisp and execute it."
+	initialPrompt := session.BuildStartupPrompt(session.BeaconConfig{
+		Recipient: fmt.Sprintf("%s/witness", rigName),
+		Sender:    "deacon",
+		Topic:     "patrol",
+	}, "I am Witness for "+rigName+". Start patrol: check gt hook, if empty create mol-witness-patrol wisp and execute it.")
 	command, err := config.BuildAgentStartupCommandWithAgentOverride("witness", rigName, townRoot, rigPath, initialPrompt, agentOverride)
 	if err != nil {
 		return "", fmt.Errorf("building startup command: %w", err)