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.

CHANGELOG.md

@@ -5,6 +5,7 @@ All notable changes to Noema are recorded here. Format follows Keep a Changelog;
 ## [Unreleased]
 
 ### Added
+- Phase 5 memory: episodic/semantic/procedural/autobiographical memory with epistemic status, fused retrieval with inspectable component scores, optional pgvector embeddings, decay without deletion, attention-gated encoding, retrieval process, memory explorer and CLI.
 - Phase 4 cognition core: deterministic attention scoring with inspectable breakdowns, global workspace and working memory with decay, per-mind cognitive runtime with bounded concurrent processes, loop detection, operator controls, live workspace page and CLI.
 - Phase 3 events: append-only cognitive event store with provenance links, filtered queries, durable cursors, live SSE streams with resume, forensic event explorer UI, thought stream page, operator observations and CLI.
 - Phase 2 minds: structured personalities with append-only version history, diff, restore, templates with preserved overrides, self-model, mind lifecycle (create, clone, disable, archive), API, UI editor and CLI.