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>
2a789c8440