feat(clustering): campaign-clusterer worker + bus topics + CLI

The campaign clusterer worker mirrors the identity-side worker shell
(bus connect, heartbeat, control listener, slow-tick fallback) but
wakes on identity.> instead of attacker.> — campaign-level work is
gated on identity-layer changes, not raw observations.

The connected-components implementation reads identities via
list_identities_for_clustering, projects them with from_identity_row,
runs union-find over combined_campaign_weight, writes campaigns rows,
sets attacker_identities.campaign_id, and runs the same revocable-
merge pass as the identity layer (a merged-out campaign whose
identities no longer co-cluster with the winner gets revoked).

Bus: adds campaign.> family (formed / identity.assigned / merged /
unmerged) plus the cross-family identity.campaign.assigned so
existing identity-stream subscribers see the badge update without
having to subscribe to campaign.>. Wiki Service-Bus.md updated in
wiki-checkout in the same wave per the project's bus-signals
discipline.

CLI: decnet campaign-clusterer registered as master-only via
MASTER_ONLY_COMMANDS; --poll-interval / --daemon mirror the identity
clusterer command surface.

decnet/clustering/campaign/base.py

@@ -0,0 +1,66 @@
+"""Campaign clusterer protocol — layer above identity resolution.
+
+Mirrors :mod:`decnet.clustering.base` for the layer above. Each concrete
+campaign clusterer implements :class:`CampaignClusterer`; callers obtain
+the active instance via
+:func:`decnet.clustering.campaign.factory.get_campaign_clusterer`.
+
+The result shape parallels :class:`ClusterResult` but speaks campaign
+vocabulary: campaigns formed, identities assigned, campaigns merged,
+campaigns unmerged.
+"""
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass, field
+from typing import Any
+
+from decnet.web.db.repository import BaseRepository
+
+
+@dataclass
+class CampaignClusterResult:
+    """Side-effects produced by a single campaign-clusterer ``tick``.
+
+    Consumed by the worker shell to publish on the bus
+    (``campaign.formed`` / ``campaign.identity.assigned`` /
+    ``campaign.merged`` / ``campaign.unmerged`` plus the cross-family
+    ``identity.campaign.assigned``).  DB writes are already committed
+    by the time this returns.
+    """
+
+    campaigns_formed: list[dict[str, Any]] = field(default_factory=list)
+    """``{"campaign_uuid": str, "identity_uuids": [str, ...]}``."""
+
+    identities_assigned: list[dict[str, Any]] = field(default_factory=list)
+    """``{"campaign_uuid": str, "identity_uuid": str,
+    "prior_campaign_uuid": Optional[str]}``."""
+
+    campaigns_merged: list[dict[str, Any]] = field(default_factory=list)
+    """``{"winner_uuid": str, "loser_uuid": str}``."""
+
+    campaigns_unmerged: list[dict[str, Any]] = field(default_factory=list)
+    """``{"resurrected_uuid": str, "former_winner_uuid": str}``."""
+
+
+class CampaignClusterer(ABC):
+    """Abstract campaign clusterer.
+
+    Single-method contract mirroring :class:`Clusterer`: ``tick`` reads
+    identities from the repo, projects them to a campaign-level feature
+    shape, runs a clustering pass, commits ``campaigns`` rows + sets
+    ``attacker_identities.campaign_id``, and returns a
+    :class:`CampaignClusterResult` summarising side-effects.
+
+    Implementations MUST NOT raise from ``tick``: a single bad pass
+    cannot be allowed to crash the worker.
+    """
+
+    name: str
+
+    @abstractmethod
+    async def tick(self, repo: BaseRepository) -> CampaignClusterResult:
+        """Run a single campaign clustering pass."""
+
+
+__all__ = ["CampaignClusterer", "CampaignClusterResult"]