v1.4.0

[1.4.0]

Added — fleet-shared Tier 2 memory (PostgreSQL + pgvector)

• pg_memory.py — PgSemanticMemory, a drop-in PostgreSQL + pgvector
  backend for Tier 2 semantic memory, enabling the persistence half of the
  Shogunet memory mesh: several agents (or planning nodes) pointing at the
  same DSN see one consistent knowledge base. API parity with the SQLite
  SemanticMemory (store_fact / search / reinforce / decay / prune /
  get_fact / extract_entities / facts_about / related_entities /
  entity_names), so it plugs directly into
  DecisionEngine(semantic_memory=...) and MemoryManager(semantic=...).
• open_semantic_memory() factory — single storage knob for operators:
  a postgres:// or postgresql:// DSN selects PgSemanticMemory; any
  other value preserves the historical local SQLite behavior.
  DecisionEngine routes memory_db_path through it, so switching a fleet
  to shared memory is a one-line config change.
• Embedding parity — the pg backend embeds with the same deterministic
  hashing embedding as the SQLite backend, so facts written by one agent on
  one backend are retrievable with identical similarity scores by another
  agent on the other backend.
• Search pushed down to pgvector — cosine distance (<=>) is computed
  server-side (similarity = 1 - distance), with an optional HNSW index
  recipe for fleet scale documented in the module docstring.
• Fail-closed, no silent stub — construction raises with actionable
  instructions if psycopg2 is missing (pip install 'shugocore[postgres]')
  or the pgvector extension is unavailable (CREATE EXTENSION vector;).
  A fleet-shared memory that quietly failed to persist would violate the
  Tier 2 invariants, so none exists.
• postgres optional dependency — pip install 'shugocore[postgres]'
  installs psycopg2-binary; no new required dependencies for existing users.

Hardened — fleet memory boundary

• Table identifiers (table_prefix) are strictly validated
  (^[a-z][a-z0-9_]{0,40}$) before interpolation into DDL/DML.
• Tier 2 only: the pg store never touches Tier 0/1 (per-agent) or Tier 3
  (read-only identity), preserving the memory invariants (N0-N1) across the
  fleet.