feat: fn_operations library — entities, relations, types_snapshot con FTS y ciclos

Paquete Go completo con modelos (Entity, Relation, RelationInput, TypeSnapshot),
DB SQLite con WAL + FTS5 en entities, CRUD para las 4 tablas, validacion de
integridad, deteccion de ciclos solo en relaciones causales (via != ''), y
operaciones de alto nivel con snapshot automatico de tipos del registry.
9 tests, todos pasan.

fn_operations/db.go

@@ -0,0 +1,140 @@
+package fn_operations
+
+import (
+	"database/sql"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+const schemaSQL = `
+CREATE TABLE IF NOT EXISTS types_snapshot (
+	id          TEXT PRIMARY KEY,
+	version     TEXT NOT NULL DEFAULT '1.0.0',
+	lang        TEXT NOT NULL,
+	algebraic   TEXT NOT NULL CHECK(algebraic IN ('product','sum')),
+	definition  TEXT NOT NULL DEFAULT '',
+	description TEXT NOT NULL DEFAULT '',
+	snapped_at  TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS entities (
+	id          TEXT PRIMARY KEY,
+	name        TEXT NOT NULL,
+	type_ref    TEXT NOT NULL,
+	status      TEXT NOT NULL DEFAULT 'active' CHECK(status IN ('active','stale','corrupted','archived')),
+	description TEXT NOT NULL DEFAULT '',
+	domain      TEXT NOT NULL DEFAULT '',
+	tags        TEXT NOT NULL DEFAULT '[]',
+	source      TEXT NOT NULL,
+	metadata    TEXT NOT NULL DEFAULT '{}',
+	notes       TEXT NOT NULL DEFAULT '',
+	created_at  TEXT NOT NULL,
+	updated_at  TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS relations (
+	id          TEXT PRIMARY KEY,
+	name        TEXT NOT NULL,
+	from_entity TEXT NOT NULL DEFAULT '',
+	to_entity   TEXT NOT NULL,
+	via         TEXT NOT NULL DEFAULT '',
+	description TEXT NOT NULL DEFAULT '',
+	purity      TEXT NOT NULL DEFAULT '' CHECK(purity IN ('','pure','impure')),
+	direction   TEXT NOT NULL DEFAULT 'unidirectional' CHECK(direction IN ('unidirectional','bidirectional','inverse')),
+	weight      REAL,
+	status      TEXT NOT NULL DEFAULT 'designed' CHECK(status IN ('designed','implemented','tested','running','deprecated')),
+	started_at  TEXT,
+	ended_at    TEXT,
+	"order"     INTEGER,
+	tags        TEXT NOT NULL DEFAULT '[]',
+	notes       TEXT NOT NULL DEFAULT '',
+	created_at  TEXT NOT NULL,
+	updated_at  TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS relation_inputs (
+	id          TEXT PRIMARY KEY,
+	relation_id TEXT NOT NULL REFERENCES relations(id) ON DELETE CASCADE,
+	entity_id   TEXT NOT NULL REFERENCES entities(id),
+	role        TEXT NOT NULL,
+	"order"     INTEGER
+);
+
+CREATE VIRTUAL TABLE IF NOT EXISTS entities_fts USING fts5(
+	id,
+	name,
+	description,
+	tags,
+	domain,
+	content='entities',
+	content_rowid='rowid'
+);
+
+-- Triggers to keep entities FTS in sync
+CREATE TRIGGER IF NOT EXISTS entities_ai AFTER INSERT ON entities BEGIN
+	INSERT INTO entities_fts(rowid, id, name, description, tags, domain)
+	VALUES (new.rowid, new.id, new.name, new.description, new.tags, new.domain);
+END;
+
+CREATE TRIGGER IF NOT EXISTS entities_ad AFTER DELETE ON entities BEGIN
+	INSERT INTO entities_fts(entities_fts, rowid, id, name, description, tags, domain)
+	VALUES ('delete', old.rowid, old.id, old.name, old.description, old.tags, old.domain);
+END;
+
+CREATE TRIGGER IF NOT EXISTS entities_au AFTER UPDATE ON entities BEGIN
+	INSERT INTO entities_fts(entities_fts, rowid, id, name, description, tags, domain)
+	VALUES ('delete', old.rowid, old.id, old.name, old.description, old.tags, old.domain);
+	INSERT INTO entities_fts(rowid, id, name, description, tags, domain)
+	VALUES (new.rowid, new.id, new.name, new.description, new.tags, new.domain);
+END;
+`
+
+// DB wraps a SQLite connection for an operations database.
+type DB struct {
+	conn *sql.DB
+	path string
+}
+
+// Open opens or creates an operations database at the given path.
+func Open(path string) (*DB, error) {
+	dir := filepath.Dir(path)
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return nil, fmt.Errorf("creating db directory: %w", err)
+	}
+
+	conn, err := sql.Open("sqlite3", path+"?_foreign_keys=on")
+	if err != nil {
+		return nil, fmt.Errorf("opening database: %w", err)
+	}
+
+	if _, err := conn.Exec("PRAGMA journal_mode=WAL"); err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("setting WAL mode: %w", err)
+	}
+
+	if _, err := conn.Exec(schemaSQL); err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("applying schema: %w", err)
+	}
+
+	return &DB{conn: conn, path: path}, nil
+}
+
+// Conn returns the underlying sql.DB for transaction use.
+func (db *DB) Conn() *sql.DB {
+	return db.conn
+}
+
+// Close closes the database connection.
+func (db *DB) Close() error {
+	return db.conn.Close()
+}
+
+// Drop removes the database file.
+func (db *DB) Drop() error {
+	db.Close()
+	return os.Remove(db.path)
+}