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/ui/minds.go

@@ -97,7 +97,8 @@ func (u *UI) mindOverview(w http.ResponseWriter, r *http.Request) {
 	}
 	sm, _ := u.deps.Minds.GetSelfModel(r.Context(), m.ID)
 	st, _ := u.deps.Events.Stats(r.Context(), m.ID, time.Now().Add(-24*time.Hour))
-	u.render(w, r, "mind", m.DisplayName, map[string]any{"Mind": m, "Brief": m.Personality.Brief(), "SelfModel": sm, "Stats": st})
+	ms, _ := u.deps.Memory.Stats(r.Context(), m.ID)
+	u.render(w, r, "mind", m.DisplayName, map[string]any{"Mind": m, "Brief": m.Personality.Brief(), "SelfModel": sm, "Stats": st, "MemStats": ms})
 }
 
 func (u *UI) mindStatus(w http.ResponseWriter, r *http.Request) {