feat(emailgen): Ollama-driven fake email worker for IMAP/POP3 deckies

Second orchestrator worker (decnet emailgen) that drips persona-driven,
threaded, multi-language fake emails into running mail deckies.  Personas
live on Topology.email_personas; topology-wide language_default falls
through to any persona that doesn't pin its own.  Em-dashes are
suppressed at the prompt layer by default and only lifted for personas
explicitly marked uses_llms_heavily — em-dashes are an LLM tell and a
flat corpus of em-dashed mail is a giveaway.

EML delivery writes into /var/spool/decnet-emails/<thread>/<msg>.eml on
the mail decky via docker exec; wiring the IMAP/POP3 templates to read
from that spool (replacing the hardcoded _BAIT_EMAILS) is the next step.

decnet/cli/__init__.py

@@ -24,6 +24,7 @@ from . import (
     bus,
     db,
     deploy,
+    emailgen,
     forwarder,
     geoip,
     init,
@@ -56,7 +57,7 @@ for _mod in (
     api, swarmctl, agent, updater, listener, forwarder,
     swarm,
     deploy, lifecycle, workers, inventory,
-    web, profiler, orchestrator, reconciler, sniffer, db,
+    web, profiler, orchestrator, emailgen, reconciler, sniffer, db,
     topology, bus, geoip, init, webhook,
 ):
     _mod.register(app)