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/handlers.go

@@ -11,6 +11,7 @@ import (
 	"github.com/andydixon/noema/internal/beliefs"
 	"github.com/andydixon/noema/internal/brain"
 	"github.com/andydixon/noema/internal/conversation"
+	"github.com/andydixon/noema/internal/graph"
 	"github.com/andydixon/noema/internal/memory"
 	"github.com/andydixon/noema/internal/predictions"
 	"github.com/andydixon/noema/internal/storage"
@@ -25,6 +26,7 @@ type Handlers struct {
 	Memory        *memory.Store
 	Beliefs       *beliefs.Store
 	Conversations *conversation.Store
+	Graph         *graph.Store
 }
 
 // Register installs the handlers on a registry.
@@ -163,6 +165,8 @@ func (h Handlers) attend(ctx context.Context, c *brain.Cycle, t workspace.Though
 	item := workspace.Item{Key: "attend:" + t.Subject, Content: t.Summary, Kind: "observation", SourceEvent: ids.ID(evID)}
 	if !mem.ID.IsZero() {
 		item.Ref = string(mem.ID)
+		text, _ := t.Content["text"].(string)
+		h.linkEntities(ctx, c, entitiesFromText(text), "", ids.ID(evID), map[string]ids.ID{"memory": mem.ID})
 	}
 	c.Runtime.Hold(item)
 	return nil