fix(prime): update sling prompts to use gt prime --hook

Polecats weren't getting full role context (including IDLE POLECAT
HERESY guidance) because start prompts said `gt hook` instead of
`gt prime --hook`. The SessionStart hook already runs `gt prime --hook`,
but manual nudge messages were inconsistent.

Changed:
- sling_helpers.go: nudge message now says `gt prime --hook`
- startup.go: assigned beacon now says `gt prime --hook`
- startup_test.go: updated test expectation

Fixes: hq-iqyu9

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/sling_helpers.go

@@ -319,7 +319,7 @@ func injectStartPrompt(pane, beadID, subject, args string) error {
 	} else if subject != "" {
 		prompt = fmt.Sprintf("Work slung: %s (%s). Start working on it now - no questions, just begin.", beadID, subject)
 	} else {
-		prompt = fmt.Sprintf("Work slung: %s. Start working on it now - run `gt hook` to see the hook, then begin.", beadID)
+		prompt = fmt.Sprintf("Work slung: %s. Start working on it now - run `gt prime --hook` to load context, then begin.", beadID)
 	}
 
 	// Use the reliable nudge pattern (same as gt nudge / tmux.NudgeSession)

internal/session/startup.go

@@ -66,8 +66,10 @@ func FormatStartupBeacon(cfg BeaconConfig) string {
 
 	// For assigned, work is already on the hook - just tell them to run it
 	// This prevents the "helpful assistant" exploration pattern (see PRIMING.md)
+	// Use `gt prime --hook` instead of `gt hook` so polecats get full role context
+	// including THE IDLE POLECAT HERESY guidance about running `gt done`.
 	if cfg.Topic == "assigned" {
-		beacon += "\n\nWork is on your hook. Run `gt hook` now and begin immediately."
+		beacon += "\n\nWork is on your hook. Run `gt prime --hook` now and begin immediately."
 	}
 
 	// For start/restart, add fallback instructions in case SessionStart hook fails

internal/session/startup_test.go

@@ -26,7 +26,7 @@ func TestFormatStartupBeacon(t *testing.T) {
 				"<- deacon",
 				"assigned:gt-abc12",
 				"Work is on your hook", // assigned includes actionable instructions
-				"gt hook",
+				"gt prime --hook",      // full context including IDLE POLECAT HERESY
 			},
 		},
 		{