feat: add long-term memory systems with fused retrieval and memory explorer

Phase 5 (ADR-0003). pkg/concepts fixes the epistemic vocabulary
(observation, fact, memory, claim, hypothesis, belief, prediction,
assumption, inference, opinion), memory kinds and relation names.

internal/memory stores episodic, semantic, procedural and
autobiographical memories in one mind-scoped table with trust-derived
credibility, importance, salience and decaying activation. Retrieval
fuses full-text rank (any-term by default), optional pgvector similarity,
recency, activation, importance and credibility, and returns the
component scores so every recall can be explained. Decay lowers
activation and never deletes; retraction and supersession keep rows for
provenance. Relationships are constrained to one mind at insert time.
Embeddings live in a conditional pgvector table keyed by model so vector
spaces are never mixed; without an embedder the system degrades to text
and graph retrieval.

Attention gates encoding: the attend handler turns admitted observations
into episodic memories (operator changes become autobiographical ones)
with memory_created events; the retrieve process proposes recalled
memories as candidates and admitted recalls are reinforced with
memory_retrieved events carrying their scoring components.

Memory explorer UI (search with component breakdown, timeline, filters,
operator knowledge entry), memory detail with provenance, relationships,
citing events and an inaccurate-memory correction; API; noemactl memory
commands; decay and embed-missing background jobs.

internal/brain/process.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/andydixon/noema/internal/attention"
+	"github.com/andydixon/noema/internal/memory"
 	"github.com/andydixon/noema/internal/minds"
 	"github.com/andydixon/noema/internal/workspace"
 	"github.com/andydixon/noema/pkg/events"
@@ -66,6 +67,7 @@ type State struct {
 // Services are read handles processes may use. Extended per phase.
 type Services struct {
 	Events EventReader
+	Memory *memory.Store
 }
 
 // EventReader is the subset of the event store processes may call.