fix(hypatia): farm token key → secret-name (scanner FP on 'secret = …')

git-private-farm.a2ml records only the secret's NAME, but the literal
'secret = "…"' shape trips Hypatia's generic-secret detector (error-level,
fails the gate — seen on nextgen-typing#34 / oblibeny#59). Renamed the key;
no value was ever present.

https://claude.ai/code/session_01GJatEm2TVFSTBEkKXmserJ

Author: claude

.machine_readable/bot_directives/git-private-farm.a2ml

@@ -18,7 +18,7 @@ workflow = ".github/workflows/instant-sync.yml"
 workflow-present = false
 target = "hyperpolymath/.git-private-farm"
 event-type = "propagate"
-secret = "FARM_DISPATCH_TOKEN"  # secret NAME only — value lives in GitHub secrets
+secret-name = "FARM_DISPATCH_TOKEN"  # secret NAME only — value lives in GitHub secrets
 presence-gated = false
 presence-gated-note = "not applicable — no instant-sync workflow present to gate"