refactor(orchestrator): collapse decnet-emailgen.service into orchestrator

Stage 5 of the realism migration. Email generation is no longer a
separate worker / systemd unit / CLI subcommand — the orchestrator's
single tick loop covers SSH traffic, file plants, and email drops.
Going from 21 services to 20.

Worker:
- _one_tick rolls between traffic / file / email (45/45/10 weights).
  The 10% email weight at a 60s orchestrator interval produces ~one
  email per 10 minutes, close to the pre-collapse 5-minute cadence.
- get_driver_for(action) (stage 4) handles SSH vs Email dispatch.
- Quiet branches fall through so a (decky-set, persona-pool,
  mail-decky) shape that silences one branch doesn't waste the tick.
- Periodic prune covers both orchestrator_events and
  orchestrator_emails tables.

Deletions:
- deploy/decnet-emailgen.service.j2
- decnet/orchestrator/emailgen/worker.py
- decnet/cli/emailgen.py
- tests/orchestrator/emailgen/test_worker_integration.py

Renames (history-preserving):
- decnet/web/router/emailgen/ -> decnet/web/router/realism/
- tests/api/emailgen/        -> tests/api/realism/
- tests/cli/test_emailgen_*  -> tests/cli/test_realism_*

Public surface changes (clean break, pre-v1):
- API URL /api/v1/emailgen/personas -> /api/v1/realism/personas
- CLI `decnet emailgen import-personas` -> `decnet realism
  import-personas`. `decnet emailgen run` is gone — the orchestrator
  covers it.
- gating.py: emailgen master-only group replaced by realism.
- decnet-orchestrator.service.j2: DECNET_REALISM_* env block added.
- decnet.target: decnet-emailgen.service entry removed.
- frontend: PersonaGeneration.tsx fetches /realism/personas.

tests/api/realism/test_personas_api.py

@@ -0,0 +1,170 @@
+"""GET/PUT /api/v1/realism/personas — global persona pool CRUD."""
+from __future__ import annotations
+
+import json
+
+import pytest
+
+from decnet.realism import personas_pool as global_pool
+from decnet.web.router.realism.api_personas import (
+    list_personas,
+    replace_personas,
+)
+
+
+@pytest.fixture(autouse=True)
+def _reset_pool():
+    global_pool.reset_cache()
+    yield
+    global_pool.reset_cache()
+
+
+_VALID = [
+    {
+        "name": "John Smith",
+        "email": "john@corp.com",
+        "role": "COO",
+        "tone": "formal",
+        "mannerisms": ["uses 'Best regards'"],
+    },
+    {
+        "name": "Sarah Johnson",
+        "email": "sarah@corp.com",
+        "role": "PM",
+        "tone": "direct",
+        "mannerisms": ["uses bullets"],
+    },
+]
+
+
+@pytest.mark.asyncio
+async def test_list_returns_empty_when_no_pool(tmp_path, monkeypatch):
+    monkeypatch.setenv(
+        "DECNET_REALISM_PERSONAS", str(tmp_path / "missing.json"),
+    )
+    result = await list_personas(user={"uuid": "u", "role": "viewer"})
+    assert result["personas"] == []
+    assert result["path"].endswith("missing.json")
+
+
+@pytest.mark.asyncio
+async def test_list_returns_existing_pool(tmp_path, monkeypatch):
+    pool = tmp_path / "pool.json"
+    pool.write_text(json.dumps(_VALID))
+    monkeypatch.setenv("DECNET_REALISM_PERSONAS", str(pool))
+
+    result = await list_personas(user={"uuid": "u", "role": "viewer"})
+    assert len(result["personas"]) == 2
+    assert {p["email"] for p in result["personas"]} == {
+        "john@corp.com", "sarah@corp.com",
+    }
+
+
+@pytest.mark.asyncio
+async def test_replace_writes_canonical_file(tmp_path, monkeypatch):
+    dest = tmp_path / "pool.json"
+    monkeypatch.setenv("DECNET_REALISM_PERSONAS", str(dest))
+
+    result = await replace_personas(
+        body={"personas": _VALID},
+        user={"uuid": "u", "role": "admin", "username": "anti"},
+    )
+    assert len(result["personas"]) == 2
+    assert dest.exists()
+    written = json.loads(dest.read_text())
+    assert {p["email"] for p in written} == {
+        "john@corp.com", "sarah@corp.com",
+    }
+
+
+@pytest.mark.asyncio
+async def test_replace_with_empty_list_clears_pool(tmp_path, monkeypatch):
+    """Operator deliberately wiping the pool is allowed — empty list is
+    valid and means "no fleet personas, skip fleet mail deckies"."""
+    dest = tmp_path / "pool.json"
+    dest.write_text(json.dumps(_VALID))
+    monkeypatch.setenv("DECNET_REALISM_PERSONAS", str(dest))
+
+    result = await replace_personas(
+        body={"personas": []},
+        user={"uuid": "u", "role": "admin", "username": "anti"},
+    )
+    assert result["personas"] == []
+    assert json.loads(dest.read_text()) == []
+
+
+@pytest.mark.asyncio
+async def test_replace_rejects_non_list_payload(tmp_path, monkeypatch):
+    from fastapi import HTTPException
+
+    monkeypatch.setenv(
+        "DECNET_REALISM_PERSONAS", str(tmp_path / "pool.json"),
+    )
+    with pytest.raises(HTTPException) as exc:
+        await replace_personas(
+            body={"personas": "not-a-list"},
+            user={"uuid": "u", "role": "admin", "username": "anti"},
+        )
+    assert exc.value.status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_replace_rejects_all_invalid_payload(tmp_path, monkeypatch):
+    """Sending a non-empty list where *every* entry is invalid is almost
+    certainly an operator schema mistake — fail loudly rather than
+    silently writing an empty pool."""
+    from fastapi import HTTPException
+
+    monkeypatch.setenv(
+        "DECNET_REALISM_PERSONAS", str(tmp_path / "pool.json"),
+    )
+    with pytest.raises(HTTPException) as exc:
+        await replace_personas(
+            body={"personas": [{"name": "broken", "email": "no-at-symbol"}]},
+            user={"uuid": "u", "role": "admin", "username": "anti"},
+        )
+    assert exc.value.status_code == 400
+    assert "validation" in exc.value.detail.lower()
+
+
+@pytest.mark.asyncio
+async def test_replace_drops_partially_invalid_entries(tmp_path, monkeypatch):
+    """One bad apple doesn't kill the request — invalid entries get
+    dropped, valid ones land, response shows what stuck."""
+    dest = tmp_path / "pool.json"
+    monkeypatch.setenv("DECNET_REALISM_PERSONAS", str(dest))
+
+    result = await replace_personas(
+        body={"personas": [
+            _VALID[0],
+            {"name": "broken", "email": "no-at-symbol"},
+            _VALID[1],
+        ]},
+        user={"uuid": "u", "role": "admin", "username": "anti"},
+    )
+    assert len(result["personas"]) == 2
+    assert {p["email"] for p in result["personas"]} == {
+        "john@corp.com", "sarah@corp.com",
+    }
+
+
+@pytest.mark.asyncio
+async def test_get_then_put_round_trips_through_pool(tmp_path, monkeypatch):
+    """The worker reads the same file the API writes — verify the
+    write-then-read cycle leaves the pool in the expected state."""
+    dest = tmp_path / "pool.json"
+    monkeypatch.setenv("DECNET_REALISM_PERSONAS", str(dest))
+
+    await replace_personas(
+        body={"personas": _VALID},
+        user={"uuid": "u", "role": "admin", "username": "anti"},
+    )
+    listed = await list_personas(user={"uuid": "u", "role": "viewer"})
+    assert {p["email"] for p in listed["personas"]} == {
+        "john@corp.com", "sarah@corp.com",
+    }
+    # And the worker's loader sees the same data.
+    loaded = global_pool.load()
+    assert {p.email for p in loaded} == {
+        "john@corp.com", "sarah@corp.com",
+    }