feat: Add mol_type schema field for molecule type classification (bd-oxgi)

Add mol_type field to beads for swarm coordination:
- Values: 'swarm' (multi-polecat), 'patrol' (recurring ops), 'work' (default)
- Nullable, defaults to empty string (treated as 'work')

Changes:
- Add mol_type column to SQLite schema and migration 031
- Add MolType type with IsValid() validation in types.go
- Update insertIssue/GetIssue to handle mol_type
- Add --mol-type flag to create command
- Add mol_type filtering to list and ready commands
- Update RPC protocol for daemon mode support
- Update test schema in migrations_test.go

🤝 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/storage/sqlite/migrations/031_mol_type_column.go

@@ -0,0 +1,34 @@
+package migrations
+
+import (
+	"database/sql"
+	"fmt"
+)
+
+// MigrateMolTypeColumn adds mol_type column to the issues table.
+// This field distinguishes molecule types (swarm/patrol/work) for swarm coordination.
+// Values: 'swarm' (multi-polecat coordination), 'patrol' (recurring ops), 'work' (regular, default)
+func MigrateMolTypeColumn(db *sql.DB) error {
+	// Check if column already exists
+	var columnExists bool
+	err := db.QueryRow(`
+		SELECT COUNT(*) > 0
+		FROM pragma_table_info('issues')
+		WHERE name = 'mol_type'
+	`).Scan(&columnExists)
+	if err != nil {
+		return fmt.Errorf("failed to check mol_type column: %w", err)
+	}
+
+	if columnExists {
+		return nil
+	}
+
+	// Add the column
+	_, err = db.Exec(`ALTER TABLE issues ADD COLUMN mol_type TEXT DEFAULT ''`)
+	if err != nil {
+		return fmt.Errorf("failed to add mol_type column: %w", err)
+	}
+
+	return nil
+}