feat: add the relationship graph with extraction, corrections and explorer

Phase 11. Entities are mind-scoped nodes with canonical matching,
aliases and deterministic kind guessing (hostnames and hyphenated ids
are systems, capitalised names people, file suffixes documents).
Relationships carry a relation from the shared vocabulary, confidence,
source, reinforcement count and the event that produced them; links tie
entities to memories, beliefs, events, goals and predictions.

The perceive and attend handlers upsert the entities a message or
observation mentions and record co-mention edges cited to the event, so
the graph grows only from what was actually seen. Operators can merge
("these are the same": edges and links move, the old name becomes an
alias, the old id still resolves), record that two entities are
different, correct kinds and add typed edges; every correction is an
operator action and a corrections row.

The explorer renders a bounded subgraph on a canvas with a small
force-directed layout in plain JavaScript, with kind filters, focus on
a neighbourhood and a side panel per entity. API, entity page, CLI and
docs/graph.md.

internal/cognition/respond.go

@@ -110,6 +110,11 @@ func (h Handlers) perceive(ctx context.Context, c *brain.Cycle, t workspace.Thou
 			claimed = append(claimed, BeliefRef{ID: res.Belief.ID, Proposition: res.Belief.Proposition, Confidence: res.Belief.Confidence, Status: string(res.Belief.Status)})
 		}
 	}
+	refs := map[string]ids.ID{"memory": memRef}
+	for _, b := range claimed {
+		refs["belief"] = b.ID
+	}
+	h.linkEntities(ctx, c, a.Entities, actor, ids.ID(srcID), refs)
 	intent := h.buildIntent(ctx, c, a, text, claimed)
 	reply, callID, err := h.generate(ctx, c, text, intent)
 	if err != nil {