feat: modelo Log y CRUD en fn_operations

Tipo Log con niveles debug/info/warn/error, source, entity_id y execution_id
opcionales. Migración 003_logs.sql y funciones InsertLog, GetLog, ListLogs
con filtros combinables.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fn_operations/migrations/003_logs.sql

@@ -0,0 +1,14 @@
+CREATE TABLE logs (
+	id           TEXT PRIMARY KEY,
+	level        TEXT NOT NULL DEFAULT 'info' CHECK(level IN ('debug','info','warn','error')),
+	source       TEXT NOT NULL DEFAULT '',
+	entity_id    TEXT NOT NULL DEFAULT '',
+	execution_id TEXT NOT NULL DEFAULT '',
+	message      TEXT NOT NULL,
+	metadata     TEXT NOT NULL DEFAULT '{}',
+	created_at   TEXT NOT NULL
+);
+
+CREATE INDEX idx_logs_level ON logs(level);
+CREATE INDEX idx_logs_source ON logs(source);
+CREATE INDEX idx_logs_created_at ON logs(created_at);

fn_operations/models.go

@@ -145,6 +145,28 @@ type AssertionResult struct {
 	EvaluatedAt time.Time             `json:"evaluated_at"`
 }
 
+// LogLevel represents the severity of a log entry.
+type LogLevel string
+
+const (
+	LogDebug LogLevel = "debug"
+	LogInfo  LogLevel = "info"
+	LogWarn  LogLevel = "warn"
+	LogError LogLevel = "error"
+)
+
+// Log is a free-form operational event within a project context.
+type Log struct {
+	ID          string         `json:"id"`
+	Level       LogLevel       `json:"level"`
+	Source      string         `json:"source"`       // who: agent, pipeline, reactive_loop, function name...
+	EntityID    string         `json:"entity_id"`    // optional context
+	ExecutionID string         `json:"execution_id"` // optional context
+	Message     string         `json:"message"`
+	Metadata    map[string]any `json:"metadata"`
+	CreatedAt   time.Time      `json:"created_at"`
+}
+
 // TypeSnapshot is an immutable copy of a registry type at point of use.
 type TypeSnapshot struct {
 	ID          string    `json:"id"`

fn_operations/store.go

@@ -814,3 +814,92 @@ func scanAssertionResults(rows *sql.Rows) ([]AssertionResult, error) {
 	}
 	return result, nil
 }
+
+// --- Log CRUD ---
+
+// InsertLog inserts a log entry.
+func (db *DB) InsertLog(l *Log) error {
+	if l.CreatedAt.IsZero() {
+		l.CreatedAt = time.Now().UTC()
+	}
+
+	_, err := db.conn.Exec(`
+		INSERT INTO logs (id, level, source, entity_id, execution_id, message, metadata, created_at)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
+		l.ID, string(l.Level), l.Source, l.EntityID, l.ExecutionID,
+		l.Message, marshalJSON(l.Metadata), l.CreatedAt.Format(time.RFC3339),
+	)
+	return err
+}
+
+// GetLog returns a log entry by ID.
+func (db *DB) GetLog(id string) (*Log, error) {
+	row := db.conn.QueryRow(`
+		SELECT id, level, source, entity_id, execution_id, message, metadata, created_at
+		FROM logs WHERE id = ?`, id)
+
+	var l Log
+	var metadataJSON, createdAt string
+	err := row.Scan(&l.ID, &l.Level, &l.Source, &l.EntityID, &l.ExecutionID,
+		&l.Message, &metadataJSON, &createdAt)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("scanning log: %w", err)
+	}
+	l.Metadata = unmarshalJSON(metadataJSON)
+	l.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
+	return &l, nil
+}
+
+// ListLogs returns logs filtered by level, source, entity, and/or execution.
+func (db *DB) ListLogs(level LogLevel, source, entityID, executionID string, limit int) ([]Log, error) {
+	where := []string{}
+	args := []any{}
+	if level != "" {
+		where = append(where, "level = ?")
+		args = append(args, string(level))
+	}
+	if source != "" {
+		where = append(where, "source = ?")
+		args = append(args, source)
+	}
+	if entityID != "" {
+		where = append(where, "entity_id = ?")
+		args = append(args, entityID)
+	}
+	if executionID != "" {
+		where = append(where, "execution_id = ?")
+		args = append(args, executionID)
+	}
+
+	q := `SELECT id, level, source, entity_id, execution_id, message, metadata, created_at FROM logs`
+	if len(where) > 0 {
+		q += " WHERE " + strings.Join(where, " AND ")
+	}
+	q += " ORDER BY created_at DESC"
+	if limit > 0 {
+		q += fmt.Sprintf(" LIMIT %d", limit)
+	}
+
+	rows, err := db.conn.Query(q, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []Log
+	for rows.Next() {
+		var l Log
+		var metadataJSON, createdAt string
+		if err := rows.Scan(&l.ID, &l.Level, &l.Source, &l.EntityID, &l.ExecutionID,
+			&l.Message, &metadataJSON, &createdAt); err != nil {
+			return nil, fmt.Errorf("scanning log: %w", err)
+		}
+		l.Metadata = unmarshalJSON(metadataJSON)
+		l.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
+		result = append(result, l)
+	}
+	return result, nil
+}